🐛 Check upstream issue before creating logbook in pr-logbook skill

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Teaches the pr-logbook skill to reuse an existing upstream feature issue as the logbook surface instead of spawning a redundant ticket. Implements #95 — the friction it reports is fixed by this very PR, which applies the new rule to itself.

How to read this PR?

1. Start with community-config/skills/pr-logbook/SKILL.md — that is the canonical tree. Read §4 Logbook entries (the only block that changed); the new pre-flight scan for Closes #N / Fixes #N / Resolves #N sits there.
2. The .claude/skills/pr-logbook/SKILL.md and .gemini/skills/pr-logbook/SKILL.md files mirror the same diff for each harness. Spot-check that the three trees stayed in sync.
3. Note the metadata.version bump (1.1.0 → 1.1.1) in all three files — that is the cheap signal downstream consumers diff against to detect the contract change.
4. The rest of the branch's commit log (pr-reviewer, developer skill tweaks) belongs to earlier merged PRs and is not part of this changeset.

How to test this PR?

1. git fetch origin && git checkout fix/issue-95-pr-logbook-upstream-check.
2. git diff main...HEAD -- '*/pr-logbook/SKILL.md' — confirm the three mirrors carry the identical +13/-1 block and the version bump.
3. Open one of the SKILL.md files at §4 and read the new clause as if you were an agent: it must be unambiguous that scanning the PR body for Closes #N / Fixes #N / Resolves #N happens before any gh issue create.
4. Cross-check Friction cluster: pr-logbook-redundant-issue (1 report) #95 — the logbook narrative for this PR lives as a comment on the issue (no sibling logbook issue was opened) and the logbook label is present. That is the live regression test.

Detailed description (for agents)

• Scope. Single behavioural edit to the pr-logbook skill, replicated across three trees (community-config/, .claude/, .gemini/). No code paths, no scripts, no agent definitions touched.
• Diff shape. Each file gains a 13-line block immediately above the existing "A logbook is not a status update" paragraph in §4, and the metadata.version line moves from "1.1.0" to "1.1.1". git diff --stat reports +13/-1 per file.
• Contract. Before opening a new logbook issue, the agent MUST scan the PR body for Closes #N, Fixes #N, or Resolves #N. If a match exists: (a) append the logbook entry as a comment on issue #N via add_issue_comment (or gh issue comment), (b) ensure #N carries the logbook label, adding it via gh issue edit <N> --add-label logbook if absent, (c) do NOT create a standalone logbook issue. Standalone issues remain valid only when no upstream ticket exists (hotfix, dependency bump, ticketless automation run).
• Self-application. This PR is its own regression test. Issue Friction cluster: pr-logbook-redundant-issue (1 report) #95 already exists (the friction report that motivated the change); the logbook entry for this work is posted as a comment on Friction cluster: pr-logbook-redundant-issue (1 report) #95 and the logbook label was added to it. No new logbook issue was created.
• Backward compatibility. Pure additive guard before the existing logbook-authoring guidance. Agents that ignore the new clause still produce valid output — they just produce the suboptimal output that the friction report flagged. The version bump is the discovery surface.
• Out of scope. Tooling to auto-detect Closes #N and route the comment without an agent decision; cross-skill propagation to pr-reviewer or developer. Both deferred until a second friction report justifies them.

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Verdict: APPROVE-equivalent (posted as COMMENT — GitHub blocks self-approval)

Independent cold-start review by the pr-reviewer agent. No authoring context.

Correctness

Each of the three SKILL.md mirrors (community-config/, .claude/, .gemini/) gains an identical 13-line block in §4 Logbook entries, positioned immediately above the "A logbook is not a status update" paragraph. The block instructs the agent to scan the PR body for Closes #N / Fixes #N / Resolves #N before creating a new logbook issue, and to append a comment + ensure the logbook label if a feature ticket exists.

The three trees stayed in sync. metadata.version correctly bumps 1.1.0 → 1.1.1 in all three files, matching AGENTS.md's convention of signalling contract changes via a version bump.

Convention compliance

• Title — Gitmoji format respected: 🐛 Check upstream issue before creating logbook in pr-logbook skill. The 🐛 emoji matches the framing.
• PR body — All four required sections present.
• Branch name — fix/issue-95-pr-logbook-upstream-check follows the fix/ prefix convention.
• Language — English throughout.
• Logbook — The PR claims #95 carries the logbook entry as a comment with the logbook label, applying the new rule to itself. Intended dogfood test.
• Version bump rule — Honoured in all three mirrors.

Test coverage

No automated tests apply (skill content is prose). The live regression test is the self-application: the PR's logbook posted as a comment on #95 rather than a sibling issue. The diff is its own fixture.

Linter findings

• lint-markdown.sh community-config/skills/pr-logbook/SKILL.md — exit 0, no output.
• lint-skill.sh community-config/skills/pr-logbook/SKILL.md (BASE_REF=main) — exit 0, no output. Confirms required frontmatter fields and the version bump vs main.

Nits (non-blocking)

• The new block names add_issue_comment (correct MCP tool) with gh issue comment as parenthetical fallback. Consider explicitly noting the MCP tool is preferred per the org's GitHub-MCP-priority rule. Minor.
• Out-of-scope items (auto-detect tooling, cross-skill propagation to pr-reviewer / developer) are appropriately deferred.

Clean change, narrow blast radius, additive guard, self-validating. Ready to merge.