feat(fixtures): add complete fixture suites for 6 tasks across 3 topics

[devin-ai-integration]

feat(fixtures): add fixture suites for 6 tasks across 3 topics

Summary

Adds complete fixture suites for 6 tasks across 3 topics, with all 4 agents (architect, planner, coder, reviewer) implemented for each task:

api-design-and-versioning

• task-1501-non-breaking-additive-change: Adding optional query param and response field
• task-1502-api-deprecation-and-v2: Deprecating v1 field and introducing v2 endpoint

database-migrations

• task-1601-add-column-with-backfill: Safe multi-step migration (add nullable → backfill → enforce NOT NULL)
• task-1602-table-split-with-compat: Splitting table with dual-write compatibility window

config-and-feature-flags

• task-1701-feature-flagged-rollout: Dark mode feature behind ENABLE_DARK_MODE flag
• task-1702-environment-specific-bugfix: Fixing staging-only API_TIMEOUT config

Each fixture includes prompt.md, expected.json/expected.patch, and verify.ts with scenario-specific semantic checks. All 24 fixtures pass npm run verify.

Review & Testing Checklist for Human

• Verify expected.json files conform to their respective Zod schemas (architect, planner, reviewer)
• Check that expected.patch files represent reasonable coder output for each scenario
• Review verify.ts semantic checks for appropriateness - particularly the substring matching logic (e.g., task-1702 had a bug where ".env" matched "environment")
• Confirm prompts accurately describe task requirements and constraints
• Verify no forbidden paths (dist/, node_modules/, .swarm/, build/, .git/) appear in patches

Test Plan:

1. Run npm run verify and confirm all 24 new fixtures show OK
2. Run npm run ci to ensure full CI passes
3. Spot-check a few expected.json files against the schema definitions in src/schemas/

Notes

These fixtures are synthetic/illustrative - they don't include repo/ directories with actual source files. The patches demonstrate expected output format rather than applying to real code.

Link to Devin run: https://app.devin.ai/sessions/c8f01518a840497dbcfb39d000259d82
Requested by: oddessentials (admin@oddessentials.com) / @oddessentials

[devin-ai-integration]

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