refactor(agents): unify dual-backend gadget builders and prompt functions

[aaight]

Summary

Refactors the dual-backend agent architecture to eliminate code duplication between the llmist backend (agents/base.ts) and the Claude Code backend (backends/agent-profiles.ts).

Card: https://trello.com/c/aLAQMmke/49-find-top-candidate-for-refactoring-and-plan-clean-refactoring-of-it-look-for-god-classes-modules-functions-files-and-code-duplic

What was done

• Gadget unification (Step 2): Extracted buildWorkItemGadgets(), buildReviewGadgets(), and buildPRAgentGadgets() into src/agents/shared/gadgets.ts as the single source of truth. Both backends now call these shared factories instead of maintaining separate identical builders. The old comment "Mirrors the logic in agents/base.ts getBaseAgentGadgets()" is gone because the code is now actually shared. Net: ~130 lines of duplicated gadget builders removed.

• Prompt builder consolidation (Step 1): Created src/agents/shared/taskPrompts.ts with canonical prompt builder functions (buildWorkItemPrompt, buildCommentResponsePrompt, buildReviewPrompt, buildCIResponsePrompt, buildPRCommentResponsePrompt, buildCheckFailurePrompt, buildDebugPrompt). Both agents/base.ts and backends/agent-profiles.ts now import from this module instead of each defining their own versions. Net: ~90 lines of duplicated prompt builders removed.

• process.chdir() side effect removal (Step 4): Fixed fetchDirectoryListing() in agent-profiles.ts which was using process.chdir(repoDir) as a workaround. Now passes the absolute repoDir path directly to ListDirectory, eliminating the race condition.

• Backwards compatibility: createPRAgentGadgets() is kept as a deprecated alias for buildPRAgentGadgets() to avoid breaking existing callers in the llmist agent files.

Key decisions

• Kept agent-profiles.ts thin wrapper functions (buildWorkItemTaskPrompt, etc.) that delegate to shared builders — avoids changing the AgentProfile interface which would require updating all 10+ profile objects and their tests.
• Used src/agents/shared/ as the location for shared code (not src/backends/) to avoid circular imports since backends/ already imports from agents/shared/.
• buildPRAgentGadgets is now complete (includes FileMultiEdit, VerifyChanges, GetPRChecks that were missing from the old createPRAgentGadgets), making both backends produce identical gadget sets.

Testing

• All 2202 existing tests pass
• Added 36 new tests:
  • tests/unit/agents/shared/taskPrompts.test.ts — 20 tests for all prompt builder functions
  • tests/unit/agents/shared/gadgets.test.ts — 16 tests verifying gadget factory behavior per capability flags

🤖 Generated with Claude Code

[nhopeatall]

🔍 Reviewing PR...

[nhopeatall]

Summary

LGTM — clean deduplication refactoring that extracts shared gadget builders and prompt functions into src/agents/shared/, eliminating ~220 lines of duplicated code between the llmist and Claude Code backends. All changes are structurally sound.

Notes

Prompt text change (intentional): The llmist backend's buildPrompt() previously included richer text ("...title, description, checklists, attachments, comments...Review it and proceed with your task.") while the Claude Code backend used a shorter version. The PR unifies to the shorter version. This is a minor behavioral change for the llmist path but is consistent with the stated goal of making both backends produce identical outputs.

Gadget set expansion (intentional, correct): createPRAgentGadgets() (now buildPRAgentGadgets()) gains FileMultiEdit, VerifyChanges, and GetPRChecks that agent-profiles.ts already had. The three llmist agent files (respond-to-ci, respond-to-review, respond-to-pr-comment) that call the deprecated alias will now get these additional gadgets — this is the intended parity fix per the PR description.

process.chdir() removal: The fix is correct. ListDirectory.execute() calls path.resolve(process.cwd(), directoryPath), and since repoDir is absolute, path.resolve uses it directly regardless of cwd. The race condition is eliminated.

Backwards compatibility: createPRAgentGadgets is kept as a thin deprecated alias, and the three existing callers in src/agents/ continue to work unchanged.

Tests: 36 new tests cover all shared builders with proper mocking. CI passes (4/4 checks green).

[nhopeatall]

Review completed - see previous review submission.