🐛 Specify logbook closing lifecycle in AGENTS.md and pr-logbook skill

[hcross]

Implements #103. Codifies who closes a logbook issue and when, so the lane does not silently accumulate stale open issues after merge.

How to read this PR?

Single commit, four files, all documentation:

1. AGENTS.md — three-line clause added to the Logbook Issues section stating that the logbook issue must be closed (state_reason: completed) once its PR is merged and any linked feature issue is closed. This is the human-facing rule.
2. community-config/skills/pr-logbook/SKILL.md — canonical source. New §7 "Post-merge cleanup" describes the close procedure (gh CLI + GitHub MCP variants) and the §4-path exception. provenance.version bumped per community-config/FORMAT.md.
3. .claude/skills/pr-logbook/SKILL.md and .gemini/skills/pr-logbook/SKILL.md — vendor mirrors of the canonical source, kept in lockstep.

The §4-path exception matters: when the PR closes an upstream feature issue (the path #95 introduced), the logbook entry lives as a comment on that issue, so closing the feature issue covers it — no separate close needed.

How to test this PR?

git fetch origin
git switch fix/issue-103-logbook-closing-lifecycle
git diff main...HEAD --stat   # expect 4 files, +57/−3
grep -n "Once the PR is merged" AGENTS.md
grep -n "Post-merge cleanup" community-config/skills/pr-logbook/SKILL.md
grep -n "Post-merge cleanup" .claude/skills/pr-logbook/SKILL.md
grep -n "Post-merge cleanup" .gemini/skills/pr-logbook/SKILL.md
task check-skill-versions   # confirms the provenance.version bump on the canonical source

Expected: each grep returns one hit per file; the version check passes (the canonical pr-logbook SKILL.md carries the bump in the same diff).

Detailed description (for agents)

• AGENTS.md — three new lines at the end of Logbook Issues establishing the close rule. Wording deliberately matches the §7 SKILL phrasing so the two sources stay synonymous.
• community-config/skills/pr-logbook/SKILL.md — new §7 "Post-merge cleanup". Two-step procedure: (1) close the logbook issue with gh issue close <n> --reason completed or the GitHub MCP issue_write tool with state: "closed" and state_reason: "completed"; (2) if the PR also closed a feature issue (via Closes #N / Fixes #N / Resolves #N), verify GitHub's auto-close fired rather than assume. Includes the §4-path exception: skip step 1 when the logbook entry was a comment on an existing feature issue. provenance.version bumped (PATCH — friction-driven clarification, no contract break).
• .claude/skills/pr-logbook/SKILL.md and .gemini/skills/pr-logbook/SKILL.md — identical §7 added; vendor mirrors track the canonical source so each harness reads the same contract.

This PR itself follows the §4-path: the logbook entry was posted as a comment on the upstream issue (#103) and the logbook label was applied there. Post-merge action (eating its own dogfood for §7): close #103 with state_reason: completed once this PR merges.

[hcross]

Independent review — cold start

(Posted as COMMENT because GitHub refuses self-approval; the verdict below is functionally Approve — no blocking issues.)

Correctness

The change does what the PR body claims: adds a closing-lifecycle rule for logbook issues to both the human-facing contract (AGENTS.md) and the operational procedure (pr-logbook/SKILL.md).

• AGENTS.md — three-line clause added directly under the existing Logbook Issues section. Correct insertion point.
• Canonical community-config/skills/pr-logbook/SKILL.md — new §7 Post-merge cleanup placed after §6 Pre-push sanity checks and before the cross-cutting version-bump section. Consistent with the existing numbered-step model.
• The §4-path exception is logically sound: when the logbook entry was appended as a comment on an upstream feature issue (the path codified by #95), closing the feature issue subsumes the logbook-close obligation. No duplicated work, no orphan issues.
• Both gh issue close --reason completed and the GitHub MCP issue_write variants (state: "closed" + state_reason: "completed") are documented — matches the dual-tooling pattern used elsewhere in the skill.

Convention compliance

• Commit title uses Gitmoji 🐛 — matches AGENTS.md §Commit Convention.
• PR body follows the four-section template (intro / read / test / detailed). Two-sentence intro respected.
• Branch name fix/issue-103-logbook-closing-lifecycle matches the documented fix/ prefix.
• Vendor mirrors .claude/skills/pr-logbook/SKILL.md and .gemini/skills/pr-logbook/SKILL.md updated in lockstep with the canonical source — verified by diff (identical §7 block, identical version bump).
• provenance.version bumped 1.1.2 → 1.1.3 across all three SKILL.md files. PATCH is the right level for an additive clarification with no contract break.
• Linked issue: #103 exists, carries the logbook label, and the PR body explicitly notes the §4-path treatment (dogfooded — logbook entry posted as a comment on #103).

Test coverage

Documentation-only change; no executable surface to test. The task check-skill-versions invocation in the test plan is the right verification — it confirms the canonical SKILL bump is in the same diff.

Linter findings

• lint-markdown.sh AGENTS.md community-config/skills/pr-logbook/SKILL.md → exit 0, no output.
• lint-skill.sh community-config/skills/pr-logbook/SKILL.md → exit 0, no output.

Verdict

Approve. Minimal, internally consistent across the three mirrors, lands the rule in the two correct surfaces (contract + procedure), correctly carves out the §4 exception. No blocking issues.

One forward-looking, non-blocking observation: once #42 (auto-fix mode) lands, the §7 close step is a natural candidate for automation by the pr-logbook agent after squash-merge — worth tracking as a follow-up.