FEAT-85: Add GENERATE_PRD command to desktop loop handler

[shafty023]

• Add GENERATE_PRD to LoopCommand, VALID_COMMANDS, and LocalJobCommand
• Create writeArtifactsForGeneratePrd to write context pack files (prompt.md, repo-info.json, artifacts/) under worktreeDir/.claude/context/
• Create readGeneratePrdOutputs to read prd.md from worktree root and return { prd: { content } } matching generatePrdUploadSchema
• Add dedicated worktree branch namespace (symphony/generate-prd-) with always-fresh creation to avoid collisions with PLAN/EXECUTE
• Add prompt validation (400 for missing/empty/non-string prompt)
• Spawn claude with write-capable tools and cwd: worktreeDir
• Add cleanupGeneratePrdWorktree helper for worktree removal on both success and failure paths, including pre-spawn early returns
• Add 7 integration tests covering rejection, context pack layout, upload shape, no-output path, and worktree cleanup

Testing: TypeScript compiles clean, 7/7 new tests pass, 5/5 SSRF regression tests pass

Risks: None identified -- new command path only, existing commands untouched

[thadeusb]

Something like this got refactored in #30

good to synchronize on the correct one-true-way to do this.

[thadeusb]

one nit about two prs adding very similar funcs

[closedloop-ai-stage]

Code Review Summary

Status: Needs Attention

Reviewers: Bug Hunter A, Bug Hunter B, Unified Auditor, Premise Reviewer, Gateway Core Architect

Findings

Severity	Count
Blocking	0
High	1
Medium	4

HIGH Issues (should fix)

1. [P1] [apps/desktop/src/main/job-store.ts:10] Missing version bump in apps/desktop/package.json - CI will fail

MEDIUM Issues (consider)

1. [P2] [apps/desktop/src/server/operations/symphony-loop.ts:1150] Inline stale-worktree removal duplicates cleanupGeneratePrdWorktree
2. [P2] [apps/desktop/test/symphony-loop-generate-prd.test.ts:674] waitForRequest resolves on started event - cleanup window starts too early (potential flakiness)
3. [P2] [apps/desktop/src/server/operations/symphony-loop.ts:1179] GENERATE_PRD worktree not cleaned up when assertPathAllowed rejects the path
4. [P2] [apps/desktop/src/server/operations/symphony-loop.ts:1146] Stale-worktree removal in GENERATE_PRD setup duplicates cleanupGeneratePrdWorktree body

Validation Stats

• Agent failures: 0 partitions skipped
• Cross-file grouped: 0 findings consolidated
• Duplicates merged: 3

Recommendation: Address the HIGH issue (missing version bump) before merging - CI will block without it. The MEDIUM issues around cleanup deduplication and test reliability are worth fixing but not blocking.