Motivation

• Fix repository TypeScript regressions so pnpm tsgo passes and prompt-building telemetry can be safely emitted.
• Make prompt contributor selection observable and deterministic for debugging/diagnostics while keeping telemetry opt-in.
• Harden work queue tooling/types so plugin API shapes and gateway parsing are enum-safe and satisfy stricter TS checks.

Description

• Prompt diagnostics and tracing: added PromptContributorDecision and PromptContributorAssemblyTrace, PromptContributorRegistry.resolveWithTrace and assembleWithTrace, and emit opt-in prompt.build diagnostic events via emitDiagnosticEvent guarded by isDiagnosticsEnabled(cfg), and wired cfg through prompt entry points (buildAgentSystemPrompt, CLI runner helpers, and commands-system-prompt).
• Diagnostic event types: extended DiagnosticEventPayload with DiagnosticPromptBuildEvent shape to carry contributors and final stage payloads.
• Prompt contributor robustness: contributors now tolerate shouldContribute/contribute failures and record selection/exclusion reasons (tag-miss, veto, errors, empty sections) and section sizes in traces.
• Workq typing and gateway parsing: introduced asEnumOrList for enum-safe status/priority parsing in gateway handlers and added explicit unknown intermediate casts for SQLite row results to satisfy TS checks.
• Workq tools: added required label fields to all workq tool definitions so they satisfy AnyAgentTool typing; fixed tests/mocks to use ClaimResult/FilesResult and include getById in DB mocks.
• Test/schema fixes: updated pi-tool-definition-adapter tests to use Type.Object(...) schemas (TypeBox) instead of raw JSON objects; fixed reviewer typing by adding ReviewerAssignment and aligning tests; fixed nullable access patterns in legacy config migration (dm?.policy, dm?.allowFrom).
• Minor CLI wiring: pass cfg into buildAgentSystemPrompt callers (embedded/CLI path) to enable gated diagnostics.

Testing

• Ran pnpm tsgo and it completed successfully (TypeScript checks pass).
• Ran targeted unit tests: pnpm test extensions/issue-tracking/src/reviewers.test.ts extensions/issue-tracking/src/local-md-provider.test.ts extensions/workq/src/cli.test.ts extensions/workq/src/tools.test.ts src/agents/pi-tool-definition-adapter.test.ts src/agents/system-prompt.test.ts src/agents/prompt-contributors/registry.test.ts and all test files passed (80 tests across those suites passed).
• Ran pnpm check (format + typecheck) which passes for the modified files, but lint (oxlint) still reports pre-existing repository-wide unused-import/unused-var issues in unrelated apps/web* files; these are not introduced by this change and remain outside the scope of this PR.

Codex Task