ci: poll review statuses from artifacts dynamically

The live comment poller previously got its review status payloads from
two sources: (1) REVIEW_STATUSES env var, frozen at comment-live job
start from needs.*.outputs.review_status, and (2) a single ci-timings
artifact fetched at the end. This meant status details (error messages,
action_required items, etc.) only appeared in the comment after all
jobs finished, even though job pass/fail was visible in real-time.

Now every status-producing workflow_call uploads a small review-status
artifact (review-status-<name>) as soon as it completes. The poller
enumerates all review-status-* artifacts across the orchestrator run
and all sub-workflow runs every cycle, downloads each, and merges them
into the comment. Statuses appear as soon as each job finishes, not
just at the end.

Changes:
- live_comment.py: replace _fetch_artifact_statuses (single artifact
  via gh CLI) with fetch_all_review_statuses (enumerate all
  review-status-* artifacts via API across all runs, download + parse
  each). Remove review_statuses_json parameter and --review-statuses-
  file CLI arg. Remove subprocess import (no longer shells out to gh).
- ci.yml: remove REVIEW_STATUSES env var, inline Python merger, and
  --review-statuses-file arg from the comment-live step. Rename
  ci-timings-review-status artifact to review-status-ci-timings.
- 8 workflow_call files: add a write review-status.json + upload
  artifact step after each review_status output is produced.
- test_live_comment.py: add tests for _parse_status_file (with/without
  prefix, empty, invalid, nonexistent, non-list) and _merge_statuses.

.github/workflows/lockfile-diff.yml

@@ -79,12 +79,24 @@ jobs:
 
           if [ "$CHANGED" = "true" ]; then
             CONTENT=$(cat /tmp/lockfile-diff.md | python3 -c "import sys,json; print(json.dumps(sys.stdin.read()))")
-            STATUS="[{\"source\":\"lockfile-diff\",\"results\":[{\"kind\":\"action_required\",\"title\":\"package-lock.json\",\"summary\":\"Locked npm dependency versions changed.\",\"detail\":${CONTENT},\"how_to_fix\":\"Add the \`ci-reviewed\` label after verifying the version changes are expected.\"}]}"
+            STATUS="[{\"source\":\"lockfile-diff\",\"results\":[{\"kind\":\"action_required\",\"title\":\"package-lock.json\",\"summary\":\"Locked npm dependency versions changed.\",\"detail\":${CONTENT},\"how_to_fix\":\"Add the \`ci-reviewed\` label after verifying the version changes are expected.\"}]}]"
           else
             STATUS="[]"
           fi
 
           echo "review_status=${STATUS}" >> "$GITHUB_OUTPUT"
+          echo "review_status=${STATUS}" > review-status.json
+
+      - name: Upload review status artifact
+        if: always() && steps.emit-status.outcome != 'skipped'
+        continue-on-error: true
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
+        with:
+          name: review-status-lockfile-diff
+          path: review-status.json
+          retention-days: 1
+          overwrite: true
+          if-no-files-found: ignore
 
       - name: Upload diff artifact
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7