Skill: Lint-catalog review on a PR

Run the infra/lint/ catalog review (./infra/pre-commit.py --review)
over a pull request's branch diff and surface every finding — as file:line
inline review comments where the finding's line is available, and as a
single fallback comment for the rest.

Your contract

You are running the review and reporting its output. You are read-only except
for posting comments: never edit, stage, commit, push, or "fix" anything, and
never run a state-changing git/gh command. The review's own lane agents are
already locked read-only.

Report the findings faithfully. The --review run (its lanes + composer) is
the authority on what is a finding: post each surviving finding verbatim —
one comment per finding. Do not drop, merge, reword the substance of, soften,
re-judge, or invent findings. Silently losing a real finding is the one
unforgivable error; so is fabricating one.

Steps

1. Idempotency guard (only with --comment). Check whether this skill has
   already posted on the PR: look for the marker <!-- marin-lint-review --> in
   both issue comments (gh pr view <PR> --json comments) and inline review
   comments (gh api repos/{owner}/{repo}/pulls/<PR>/comments --paginate). If the
   marker is present, stop now — the PR already has a lint pass and we do not want
   duplicate comments. Otherwise continue.

2. Run the review. From the repo root:

   head_sha="$(git rev-parse HEAD)"
   MARIN_REVIEW_TRIGGER=ci \
     MARIN_REVIEW_PR_NUMBER=<PR> \
     MARIN_REVIEW_HEAD_SHA="$head_sha" \
     ./infra/pre-commit.py --review --agent-command='codex exec'

   The command writes its raw per-arm prompts/outputs and the
   combined findings under /tmp/marin-linter/<branch>/<timestamp>-<uniq>/ (path printed at the
   end); read it if a run looks wrong.

3. Collect the findings. Each finding the command emits on stdout is one line
   in the canonical catalog format:

   <path>:<line>: ml-<code> (<confidence>) <message>

   e.g. lib/iris/src/iris/foo.py:42: ml-cruft-dead-branch (0.85) Unreachable else after early return.

4. No findings vs. failed run. Distinguish two zero-finding cases:

   • Clean — the command exited 0 and printed Lint review: no findings. (or
     emitted no finding lines). Post nothing: the green job check is the "lint
     pass clean" signal, and a second "all clear" comment would only duplicate the
     high-level review. State "Lint review: no findings." to the terminal and stop.
   • Failed to run — the command exited non-zero or printed that every lane
     failed / the agent was not found / the merge-base could not be resolved. Do
     not report this as clean. State plainly in your final output that the lint
     review could not run and why; post no comments. (A broken run is a job-log
     signal, not a PR comment.)

   (Without --comment: just print the findings, if any, to the terminal and stop
   here regardless.)

5. Post inline comments. With --comment and findings present, for each
   finding post one inline comment with
   mcp__github_inline_comment__create_inline_comment, the
   finding's path and line, and a body of exactly this shape:

   `ml-<code>` · confidence <confidence>
   
   <message>
   
   <!-- marin-lint-review -->

   The <message> is copied verbatim from the finding. Post one comment per
   finding; never post two comments for the same finding.

6. Handle un-anchorable findings. The inline-comment tool rejects a line that
   is not part of the PR diff (it raises a validation error). A finding can land
   on such a line — e.g. the holistic meta lane anchors on context outside the
   added hunks. When a post fails for that reason, do not abort: record that
   finding and keep going through the rest.

7. Fallback summary. After attempting every inline comment, if any findings
   could not be placed inline, post one issue comment with gh pr comment <PR>
   so none are dropped. Format:

   Lint review:
   
   These infra/lint findings anchor on lines not in the PR diff, so they could not
   be attached inline.
   
   - <path>:<line>: ml-<code> (<confidence>) <message>
   - ...
   
   <!-- marin-lint-review -->

   List every un-anchorable finding verbatim. If every finding was placed inline,
   do not post this comment.

Notes

• Use the gh CLI for GitHub; do not web-fetch.
• The review reads the branch diff against the merge base with origin/main,
  covering committed and uncommitted work. CI checks out the PR head and fetches
  origin/main before invoking you, so the merge base resolves.