feat(agents): add GitHub backlog management pipeline

## Summary

Introduces a complete TPM-focused GitHub backlog management pipeline — 5 instructions, 4 prompts, and 1 orchestrator agent — mirroring the ADO tooling pipeline architecture with GitHub-native MCP tools. Replaces and deprecates the single-purpose `github-issue-manager` agent with a comprehensive four-stage workflow covering triage, discovery, sprint planning, and batch execution.

**Branch:** `feat/github-backlog-management-tooling`
**Commit:** `3fe2c00`
**Scope:** 19 files changed, 2,621 insertions, 477 deletions

## Motivation

The existing `github-issue-manager.agent.md` provided only conversational filing, navigation, and search for individual GitHub issues. TPMs managing GitHub backlogs needed the same rigor available for ADO work items: batch triage, duplicate detection, milestone-based sprint planning, hierarchy-aware execution, and three-tier autonomy controls. The ADO pipeline (planning → discovery → update → PR) proved the architectural blueprint; this work adapts that blueprint to GitHub's issue model.

## Architecture

**Instructions-first pipeline** (parallel to the ADO tooling suite):

```
github-backlog-planning.instructions.md (P0 — reference specification)
    ├── github-backlog-triage.instructions.md (consumes planning spec)
    ├── github-backlog-discovery.instructions.md (consumes planning spec)
    └── github-backlog-update.instructions.md (consumes planning spec)

github-backlog-manager.agent.md (orchestrator)
    ├── github-triage-issues.prompt.md → triage instructions
    ├── github-discover-issues.prompt.md → discovery instructions
    ├── github-execute-backlog.prompt.md → update instructions
    └── github-sprint-plan.prompt.md → planning spec + milestone APIs
```

Key design decisions:
- **Reference specification as foundation** — `github-backlog-planning.instructions.md` (758 lines) defines planning file templates, field conventions, MCP tool catalog, search protocols, similarity assessment matrix, state persistence, and the three-tier autonomy model. All workflow instructions cross-reference this file rather than duplicating conventions.
- **Intent-based routing** — The orchestrator agent classifies incoming requests into one of five workflow types (triage, discovery, sprint, execution, single-issue) and dispatches to the appropriate prompt via handoff configuration.
- **Three-tier autonomy** — Full (no gates), Partial (key gates only), Manual (all gates). Workflows default to Partial; users override per session.
- **Similarity assessment** — A 5-dimension matrix (title, body, labels, milestone, assignee) with weighted scoring prevents duplicate issue creation during batch operations.
- **Hierarchy-aware execution** — Batch operations process parent issues before children to maintain referential integrity with GitHub's sub-issues API.

## Changes

### New Artifacts (10 files)

#### Instructions (5)

| File | Lines | Purpose |
|------|-------|---------|
| `github-backlog-planning.instructions.md` | 758 | Reference specification: planning file templates, MCP tool catalog, search protocols, similarity assessment, state persistence, three-tier autonomy model |
| `github-backlog-triage.instructions.md` | 302 | Triage pipeline: batch label suggestion, milestone assignment, priority assessment, duplicate detection with planning file output |
| `github-backlog-discovery.instructions.md` | 234 | Discovery workflows: artifact-driven, user-centric, and search-based issue discovery with planning file generation |
| `github-backlog-update.instructions.md` | 226 | Execution pipeline: consumes planning handoffs, executes batch issue operations with hierarchy-aware ordering |
| `community-interaction.instructions.md` | 335 | Community interaction voice/tone guidelines referenced by backlog workflows for issue/PR comments |

#### Prompts (4)

| File | Lines | Purpose |
|------|-------|---------|
| `github-triage-issues.prompt.md` | 84 | Entry point for triage workflow — scopes to repo, runs label/milestone/duplicate analysis |
| `github-discover-issues.prompt.md` | 128 | Entry point for discovery — three modes (artifact-driven, user-centric, search-based) |
| `github-execute-backlog.prompt.md` | 78 | Entry point for batch execution — consumes planning handoffs, applies changes |
| `github-sprint-plan.prompt.md` | 109 | Sprint planning — milestone management, velocity analysis, capacity allocation |

#### Agent (1)

| File | Lines | Purpose |
|------|-------|---------|
| `github-backlog-manager.agent.md` | 174 | Orchestrator with intent classification, five workflow dispatch paths, handoff configuration to all four prompts |

### Modified Files (9)

| File | Change | Detail |
|------|--------|--------|
| `github-add-issue.prompt.md` | Bug fix + refactor | Fixed `mcp_github_create_issue` → `mcp_github_issue_write` (tool doesn't exist); rewrote from 304→86 lines; now delegates to `github-backlog-planning.instructions.md` for templates; maturity changed to `experimental` |
| `github-issue-manager.agent.md` | Deprecated | Content replaced with deprecation notice pointing to `github-backlog-manager.agent.md`; maturity set to `deprecated` |
| `CUSTOM-AGENTS.md` | Updated | Agent table: `github-issue-manager` → `github-backlog-manager` with updated description and workflow notes |
| `hve-core-installer.agent.md` | Updated | Agent count 14+ → 20+; agent listing updated to include `github-backlog-manager`; formatting fixes |
| `writing-style.instructions.md` | Extended | Added "Community" row to formality/pronoun tables; cross-reference to `community-interaction.instructions.md` |
| `docs/getting-started/install.md` | Reference update | `github-issue-manager` → `github-backlog-manager` |
| `docs/getting-started/mcp-configuration.md` | Reference update | Agent MCP Dependencies table updated with new agent name and description |
| `extension/README.md` | Reference update | Agent listing updated to `github-backlog-manager` |
| `extension/package.json` | Regenerated | Manifest updated: 21 agents, 26 prompts, 23 instructions |

## Validation

All validators passed on the committed artifacts:

| Validator | Result |
|-----------|--------|
| `npm run format:tables` | Clean |
| `npm run lint:frontmatter` | 127 files, 0 errors |
| `npm run lint:md` | 0 errors (fixed MD013 in agent file during validation) |
| `npm run spell-check` | 91 files, 0 issues |
| `npm run lint:md-links` | All links passed |
| `npm run extension:prepare` | 21 agents, 26 prompts, 23 instructions |

## Review Checklist

### Artifact Quality

- [ ] Planning specification covers MCP tool catalog, planning file templates, similarity assessment
- [ ] Triage instructions produce planning files with label/milestone recommendations
- [ ] Discovery instructions support all three modes (artifact, user, search)
- [ ] Update instructions consume planning handoffs with hierarchy-aware ordering
- [ ] Community interaction instructions define voice/tone for issue comments
- [ ] All four prompts correctly reference their backing instructions
- [ ] Orchestrator agent routes all five intent types to correct workflows
- [ ] Bug fix resolves non-existent `mcp_github_create_issue` tool reference

### Integration

- [ ] Deprecated `github-issue-manager` agent has clear migration notice
- [ ] All cross-repo references updated (CUSTOM-AGENTS, installer, docs, extension)
- [ ] Extension manifest registers all new artifacts
- [ ] Writing-style instructions include community interaction cross-reference

### Maturity

- [ ] All new artifacts ship at `experimental`
- [ ] Deprecated agent marked with `deprecated` maturity
- [ ] Progression to `preview` after multi-repo testing and TPM feedback

## Research

- `.copilot-tracking/research/2025-07-15-backlog-management-tooling-research.md` (851 lines)
- `.copilot-tracking/details/2026-02-05-github-backlog-tooling-details.md`
- `.copilot-tracking/plans/2026-02-05-github-backlog-tooling-plan.instructions.md`

File	Change	Detail
`github-add-issue.prompt.md`	Bug fix + refactor	Fixed `mcp_github_create_issue` → `mcp_github_issue_write` (tool doesn't exist); rewrote from 304→86 lines; now delegates to `github-backlog-planning.instructions.md` for templates; maturity changed to `experimental`
`github-issue-manager.agent.md`	Deprecated	Content replaced with deprecation notice pointing to `github-backlog-manager.agent.md`; maturity set to `deprecated`
`CUSTOM-AGENTS.md`	Updated	Agent table: `github-issue-manager` → `github-backlog-manager` with updated description and workflow notes
`hve-core-installer.agent.md`	Updated	Agent count 14+ → 20+; agent listing updated to include `github-backlog-manager`; formatting fixes
`writing-style.instructions.md`	Extended	Added "Community" row to formality/pronoun tables; cross-reference to `community-interaction.instructions.md`
`docs/getting-started/install.md`	Reference update	`github-issue-manager` → `github-backlog-manager`
`docs/getting-started/mcp-configuration.md`	Reference update	Agent MCP Dependencies table updated with new agent name and description
`extension/README.md`	Reference update	Agent listing updated to `github-backlog-manager`
`extension/package.json`	Regenerated	Manifest updated: 21 agents, 26 prompts, 23 instructions

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feat(agents): add GitHub backlog management pipeline #447

Summary

Motivation

Architecture

Changes

New Artifacts (10 files)

Instructions (5)

Prompts (4)

Agent (1)

Modified Files (9)

Validation

Review Checklist

Artifact Quality

Integration

Maturity

Research

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

File	Lines	Purpose
`github-backlog-planning.instructions.md`	758	Reference specification: planning file templates, MCP tool catalog, search protocols, similarity assessment, state persistence, three-tier autonomy model
`github-backlog-triage.instructions.md`	302	Triage pipeline: batch label suggestion, milestone assignment, priority assessment, duplicate detection with planning file output
`github-backlog-discovery.instructions.md`	234	Discovery workflows: artifact-driven, user-centric, and search-based issue discovery with planning file generation
`github-backlog-update.instructions.md`	226	Execution pipeline: consumes planning handoffs, executes batch issue operations with hierarchy-aware ordering
`community-interaction.instructions.md`	335	Community interaction voice/tone guidelines referenced by backlog workflows for issue/PR comments

File	Lines	Purpose
`github-triage-issues.prompt.md`	84	Entry point for triage workflow — scopes to repo, runs label/milestone/duplicate analysis
`github-discover-issues.prompt.md`	128	Entry point for discovery — three modes (artifact-driven, user-centric, search-based)
`github-execute-backlog.prompt.md`	78	Entry point for batch execution — consumes planning handoffs, applies changes
`github-sprint-plan.prompt.md`	109	Sprint planning — milestone management, velocity analysis, capacity allocation

Validator	Result
`npm run format:tables`	Clean
`npm run lint:frontmatter`	127 files, 0 errors
`npm run lint:md`	0 errors (fixed MD013 in agent file during validation)
`npm run spell-check`	91 files, 0 issues
`npm run lint:md-links`	All links passed
`npm run extension:prepare`	21 agents, 26 prompts, 23 instructions

feat(agents): add GitHub backlog management pipeline #447

Description

Summary

Motivation

Architecture

Changes

New Artifacts (10 files)

Instructions (5)

Prompts (4)

Agent (1)

Modified Files (9)

Validation

Review Checklist

Artifact Quality

Integration

Maturity

Research

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions