Added comprehensive Design Thinking documentation and unified the DT-to-RPI handoff pipeline. This PR established a complete nine-method framework reference under docs/design-thinking/, integrated DT into the HVE Guide lifecycle, and routed all three exit points exclusively through the Task Researcher agent. Across 35 files (17 new, 18 modified), the changes introduced 2463 lines and removed 200, closing a major documentation gap for Design Thinking adoption in hve-core.

Description

Architectural Change: Unified Exit Point Routing

All three DT exit points now route exclusively through Task Researcher, replacing the prior pattern where exits could target different RPI agents. This unified the handoff contract and simplified the integration surface.

• Updated dt-coach.agent.md to align agent configuration with unified routing
• Revised dt-rpi-handoff-contract.instructions.md to route all three exit points through Task Researcher
• Modified context instruction files (dt-rpi-implement-context, dt-rpi-planning-context, dt-rpi-research-context) for consistency with the new routing model
• Updated both handoff prompts (dt-handoff-implementation-space.prompt.md, dt-handoff-solution-space.prompt.md) to target Task Researcher exclusively

Design Thinking Documentation Suite

Established a complete framework reference with 17 new files covering the three-space model (Problem, Solution, Validation) and all nine methods.

• Added docs/design-thinking/README.md with framework overview, nine-method summary table, and RPI integration entry points
• Created nine method guides (method-01 through method-09) following an identical structural template with activities, sample prompts, expected outputs, quality checks, and RPI integration tables
• Added dt-coach.md and dt-learning-tutor.md tutorials with invocation patterns, starter prompts, and manufacturing scenario examples
• Created dt-rpi-integration.md covering exit point mapping, confidence markers (validated, assumed, unknown, conflicting), and per-agent input tables
• Added tutorial-handoff-to-rpi.md with step-by-step guidance for all three exit points using practical manufacturing scenarios
• Created using-together.md with an end-to-end walkthrough demonstrating how a dashboard request was reframed as a knowledge-loss problem through DT, then transitioned to RPI
• Added why-design-thinking.md with a comparison table against traditional requirements gathering and industry applicability

HVE Guide Lifecycle Integration

Wove Design Thinking into the existing project lifecycle framework as an optional entry point feeding into Stage 2 Discovery.

• Updated docs/hve-guide/README.md Mermaid lifecycle flowchart with a DT optional-entry node and added UX Designer to the roles table
• Modified docs/hve-guide/lifecycle/README.md to insert "Design Thinking to Stage 2" as transition rule 1, renumbering existing rules
• Expanded discovery.md Available Tools table to include dt-coach and added a "Design Thinking as Pre-Research Methodology" callout
• Added a "Design Thinking for Product Concepts" section to product-definition.md

Role Guide Updates

• Added dt-coach to Key Agents tables in business-program-manager.md and tpm.md with contextual paragraphs
• Created ux-designer.md role guide with recommended collections, five lifecycle stages mapped to DT methods, starter prompts, and do/don't tips

Navigation and Discovery

• Added Design Thinking section with navigation links to docs/README.md
• Added Design Thinking agent group entry to docs/agents/README.md
• Added "Design Thinking Path" section to docs/getting-started/README.md
• Updated plugin README descriptions in plugins/design-thinking/README.md and plugins/hve-core-all/README.md to reflect Task Researcher routing

Related Issue(s)

Closes #783

Type of Change

Select all that apply:

Code & Documentation:

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update

Infrastructure & Configuration:

• GitHub Actions workflow
• Linting configuration (markdown, PowerShell, etc.)
• Security configuration
• DevContainer configuration
• Dependency update

AI Artifacts:

• Reviewed contribution with prompt-builder agent and addressed all feedback
• Copilot instructions (.github/instructions/*.instructions.md)
• Copilot prompt (.github/prompts/*.prompt.md)
• Copilot agent (.github/agents/*.agent.md)
• Copilot skill (.github/skills/*/SKILL.md)

Note for AI Artifact Contributors:

• Agents: Research, indexing/referencing other project (using standard VS Code GitHub Copilot/MCP tools), planning, and general implementation agents likely already exist. Review .github/agents/ before creating new ones.
• Skills: Must include both bash and PowerShell scripts. See Skills.
• Model Versions: Only contributions targeting the latest Anthropic and OpenAI models will be accepted. Older model versions (e.g., GPT-3.5, Claude 3) will be rejected.
• See Agents Not Accepted and Model Version Requirements.

Other:

• Script/automation (.ps1, .sh, .py)
• Other (please describe):

Sample Prompts (for AI Artifact Contributions)

User Request:

"I have a manufacturing dashboard project. Help me run through Design Thinking before building it."

Invoke the dt-coach agent from the agent picker, then provide your project context. The coach guides you through the nine DT methods and hands off to RPI through the Task Researcher when ready.

Execution Flow:

1. User selects dt-coach from the agent picker
2. Coach begins Method 1 (Scope Conversations) and guides through Problem Space methods
3. Coach transitions through Solution Space methods (4-6) and Validation Space methods (7-9)
4. At any exit point, coach produces a structured handoff artifact
5. User invokes a handoff prompt (dt-handoff-solution-space.prompt.md or dt-handoff-implementation-space.prompt.md)
6. Task Researcher receives the handoff and begins RPI workflow with DT context

Output Artifacts:

• DT coaching session state in .copilot-tracking/dt/
• Handoff artifact with confidence markers and method evidence
• RPI research document seeded with DT findings

Success Indicators:

• Coach navigates through DT methods with contextual prompts
• Handoff artifact contains validated findings with proper confidence markers
• Task Researcher receives and processes the DT handoff without requiring manual context transfer

Testing

All changes were validated through the following checks:

• npm run lint:md — passed
• npm run spell-check — passed
• npm run lint:frontmatter — passed
• npm run validate:skills — passed
• npm run lint:md-links — passed
• npm run lint:ps — passed
• npm run plugin:generate — passed (table formatting applied to 2 files, committed separately)

Manual review confirmed consistent YAML frontmatter across all 17 new files, identical structural templates across method guides 01-09, accurate cross-references between documentation files, and correct exit point routing through Task Researcher in all modified AI artifacts.

Checklist

Required Checks

• Documentation is updated (if applicable)
• Files follow existing naming conventions
• Changes are backwards compatible (if applicable)
• Tests added for new functionality (if applicable)

AI Artifact Contributions

• Used /prompt-analyze to review contribution
• Addressed all feedback from prompt-builder review
• Verified contribution follows common standards and type-specific requirements

Required Automated Checks

The following validation commands must pass before merging:

• Markdown linting: npm run lint:md
• Spell checking: npm run spell-check
• Frontmatter validation: npm run lint:frontmatter
• Skill structure validation: npm run validate:skills
• Link validation: npm run lint:md-links
• PowerShell analysis: npm run lint:ps
• Plugin freshness: npm run plugin:generate

Security Considerations

• This PR does not contain any sensitive or NDA information
• Any new dependencies have been reviewed for security issues
• Security-related scripts follow the principle of least privilege

Additional Notes

• The unified exit point routing through Task Researcher is a breaking change for any workflow that previously targeted Task Planner or Task Implementor directly from DT exit points. Update any custom handoff workflows accordingly.
• Plugin README files (plugins/design-thinking/README.md, plugins/hve-core-all/README.md) were modified to reflect the routing change. Run npm run plugin:generate to confirm freshness.
• Table reformatting in role guides (business-program-manager.md, tpm.md) produced larger diffs due to column-width alignment changes; only the dt-coach row and contextual paragraph were substantive additions.