fix(skill): add retry guard to prevent intra-run duplicate reviews (#1322)

## Summary

- Adds explicit guidance in the `review-pr` skill to verify whether a
review was already posted before retrying a failed/stuck API call
- Prevents intra-run duplicate reviews (distinct from cross-run dedup in
#1139)

Fixes #1321

## Context

Run 22784882686 posted the same review body twice on PR #1320 (4 minutes
apart) because the bot thought the first API call was "stuck" and
retried with `gh pr review --comment` without checking if the review had
already been posted.

## Test plan

- [ ] Next external PR review should not produce duplicate reviews even
if the API call is slow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: worktrunk-bot <254187624+worktrunk-bot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: worktrunk-bot

.claude/skills/review-pr/SKILL.md

@@ -283,9 +283,16 @@ approach:
 
 #### Posting
 
-Submit **one formal review per run** via `gh pr review`. Note that `--comment`
-requires a non-empty body (`-b ""` fails) — if there's nothing to say, use the
-approve-with-empty-body pattern instead.
+Post exactly one review per run. API calls can succeed server-side while
+appearing to hang, so always verify before calling `gh pr review`:
+```bash
+gh api "repos/$REPO/pulls/<number>/reviews" \
+  --jq "[.[] | select(.user.login == \"$BOT_LOGIN\" and .commit_id == \"$HEAD_SHA\")] | last | .submitted_at // empty"
+```
+If this returns a timestamp, the review is already posted — you're done.
+Otherwise, submit via `gh pr review`. Note that `--comment` requires a non-empty
+body (`-b ""` fails) — if there's nothing to say, use the approve-with-empty-body
+pattern instead.
 
 - Always give a verdict: **approve** or **comment**. Don't use "request changes"
   (that implies authority to block).