docs(os-dev): capture gate exit status before any pipe, quote the gate's verdict line

[os-support-ai]

Fixes#9552

What this adds

A compact discipline block in the gate-running section of .claude/agents/os-dev.md (governed surface, .claude/**), stating both halves of the fix:

1. Capture-before-pipe (safe forms).EXIT=$? read after cmd 2>&1 | tail -40 captures tail's exit status, not the gate's — tail essentially always succeeds, so the read is 0 for a green gate and a red one alike. This is not merely unreliable, it is unfalsifiable: it returns the same value for both outcomes, so re-running never surfaces the defect, while it reads as a measurement in a report. Three safe forms are given, any one of which avoids the trap:
   • redirect-then-capture: cmd > /tmp/out 2>&1; EXIT=$?; tail -40 /tmp/out
   • set -o pipefail
   • ${PIPESTATUS[0]}
2. Verdict-line reporting rule. When citing a gate's result in a report, quote the gate's own printed verdict line — never a bare $?. The verdict line is written by the gate; $? after a pipe is written by your shell plumbing, and the two can disagree silently.
3. One-sentence option-3 intractability note. Mechanical enforcement of this discipline is recorded as measured-intractable: the trap lives in an agent's shell usage, not in any version-controlled artifact, so nothing can observe it structurally — no later round should re-derive that conclusion or go looking for a linter that could catch it.

Diff

.claude/agents/os-dev.md only — 11 insertions, 0 deletions, no other files touched. (Verified by inspecting git show f8edabf --stat before pushing, per takeover dispatch instructions.)

Ratchet

check:pm-skill-ratchet (os-dev.md ceiling 399): file is now 352 lines (11 lines added this commit → previously 341), headroom 47. Green, not at ceiling.

Gate results at f8edabf

Derived gate union via node scripts/pm/dispatch-gates.mjs inside the worktree — 8 local gates matched, all exit 0:

• pnpm check:agent-model-declared — GREEN (1 agent definition, os-dev.md → opus, 0 justified inherits)
• pnpm check:doc-authoring — GREEN (377 files clean)
• pnpm --filter @objectstack/lint run check:doc-formula-expressions — GREEN (22 record-scoped examples / 396 files judged clean; 9 spec-TSDoc examples judged clean)
• pnpm check:nul-bytes — GREEN (6203 text files scanned, no raw ASCII control bytes)
• pnpm check:pm-governed-merges — GREEN (self-test only, 25 assertions)
• pnpm check:pm-skill-id-lint — GREEN (9 files clean)
• pnpm check:pm-skill-ratchet — GREEN (os-dev.md 352/399; all other ratcheted files unchanged, at their pinned ceilings)
• pnpm check:skill-frame-sync — GREEN (4 copies of the decision frame structurally isomorphic)

git rev-parse --short HEAD → f8edabf

Provenance

Implementation authored earlier in this same session (session_01WswfK2yNYT9hNnMH6TzAwL), which was interrupted three times by API 529s during close-out (push + PR + report). This PR is that session resuming to complete the four mechanical close-out steps only — no reimplementation, no re-derivation of the underlying reasoning.

Governed surface

.claude/** is governed. This PR stays draft; only a human merges it. No ready/enqueue/arm transition is made or requested here.

Generated by Claude Code

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Generated by Claude Code