story-kit: create 142_bug_quality_gates_run_after_fast_forward_to_master_instead_of_before

.story_kit/work/1_upcoming/142_bug_quality_gates_run_after_fast_forward_to_master_instead_of_before.md

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+---
+name: "Quality gates run after fast-forward to master instead of before"
+---
+
+# Bug 142: Quality gates run after fast-forward to master instead of before
+
+## Description
+
+## Bug
+
+The `merge_agent_work` function in `server/src/agents.rs` runs quality gates AFTER the squash merge has already been fast-forwarded to master. This means broken code lands on master before gates catch it.
+
+### Current Flow (broken)
+1. `run_squash_merge()` creates merge-queue branch + temp worktree
+2. Squash merge + conflict resolution in temp worktree
+3. **Fast-forward master to merge-queue commit** (line 2522)
+4. Clean up temp worktree + branch
+5. `run_merge_quality_gates()` runs on master (line 1047)
+6. If gates fail, broken code is already on master
+
+### Expected Flow
+1. `run_squash_merge()` creates merge-queue branch + temp worktree
+2. Squash merge + conflict resolution in temp worktree
+3. **Run quality gates in the merge-queue worktree BEFORE fast-forward**
+4. If gates fail: tear down temp worktree + branch, leave master untouched, report failure
+5. If gates pass: fast-forward master, clean up
+
+### Key Files
+- `server/src/agents.rs` line 1013: `merge_agent_work()` — orchestrator
+- `server/src/agents.rs` line 2367: `run_squash_merge()` — does merge + fast-forward
+- `server/src/agents.rs` line 2522: fast-forward step that should happen AFTER gates
+- `server/src/agents.rs` line 1047: `run_merge_quality_gates()` — runs too late
+
+### Impact
+Broken merges (conflict markers, missing braces) land on master and break all worktrees that pull from it. Mergemaster then has to fix master directly, adding noise commits.
+
+## How to Reproduce
+
+1. Have a feature branch with code that conflicts with master
+2. Call merge_agent_work for that story
+3. run_squash_merge resolves conflicts (possibly incorrectly)
+4. Fast-forwards master to the merge-queue commit BEFORE gates run
+5. run_merge_quality_gates runs on master and finds broken code
+6. Master is already broken
+
+## Actual Result
+
+Broken code (conflict markers, missing braces) lands on master. Mergemaster then fixes master directly, adding noise commits. All active worktrees pulling from master also break.
+
+## Expected Result
+
+Quality gates should run in the merge-queue worktree BEFORE fast-forwarding master. If gates fail, master should remain untouched.
+
+## Acceptance Criteria
+
+- [ ] Bug is fixed and verified