Replace per-run no-op comments with a maintained rollup on the no-op issue

[Copilot]

Issue #39849 had become an unreadable stream of no-op comments. This change turns the issue into a maintained rollup that buckets recurring no-op causes by workflow and message, while preserving legacy history.

• Rollup the no-op issue body instead of appending comments

  • handle_noop_message.cjs now updates the [aw] No-Op Runs issue body in place.
  • The rollup summarizes:
    • total no-op runs
    • top workflows by count
    • workflow/root-cause buckets with counts and latest run links

• Seed the rollup from existing history

  • On first update, the handler scans legacy per-run comments and folds them into the new rollup state.
  • Rollup state is embedded in the issue body so subsequent runs update counts without rescanning history.

• Keep the issue template aligned with the new behavior

  • The no-op issue template now describes the issue as a maintained summary rather than a comment sink.

• Cover migration and steady-state behavior in tests

  • Updated focused tests for:
    • in-place rollup updates
    • bootstrapping from legacy comments
    • skipping bootstrap once rollup state already exists

const updatedBody = upsertNoopRollupIntoIssueBody(
  issue.body || "",
  buildNoopRollupSection(state, latestFooterLine || "")
);

await github.rest.issues.update({
  owner,
  repo,
  issue_number: noopRunsIssue.number,
  body: updatedBody,
});