Collapse superseded benchmark comments rather than prefixing them

[ms609]

GitHub can genuinely collapse a superseded comment — minimizeComment with
classifier: OUTDATED — rather than leaving it at full height behind a ⚠️
banner. The benchmark comment step now does that.

What changed

• The listing moves from issues.listComments to GraphQL, because REST's
  comment payload omits isMinimized. Minimizing no longer edits the body, so
  that flag is the only remaining idempotency guard; without it every run would
  re-minimize the entire history.
• The listing and each mutation warn rather than throw. This step exists to post
  the new result, and losing that to a hiccup while tidying up the old ones
  would be a poor trade.

Worth knowing

• Comments already carrying the old ⚠️ banner keep it, and are not minimized,
  so the first run under this code collapses them banner and all — one slightly
  ugly comment per open PR, then it is clean.
• Fork PRs still get a read-only token and the whole step no-ops there, exactly
  as before.
• This job declares no permissions: block, so its token comes from the
  repository default. minimizeComment needs write access to the comment; if
  the default proves too narrow, the run log says so and the benchmark comment
  still posts.

No NEWS.md / DESCRIPTION bump: CI plumbing is not user-visible package
behaviour.

Companion PRs apply the same change to the other repos carrying this script
(ms609/Coreset, ms609/TreeTools, ms609/TreeDist). TreeSearch's
agent-benchmark.yml is dispatch-only and uploads artifacts without commenting,
so it needs nothing.

---

Agent work, filed under @ms609's own account because the ms609-agent account
is currently suspended — so it has not had the independent review that
agent-authored PRs normally get.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.55%. Comparing base (a8fc0b7) to head (3a712cc).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #202   +/-   ##
=======================================
  Coverage   95.55%   95.55%           
=======================================
  Files          56       56           
  Lines        5045     5045           
=======================================
  Hits         4821     4821           
  Misses        224      224           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.