Release v4.9.0

Maintenance release for the v4 line

Security and dependency fixes only. The changelog output format is unchanged
from v4.8.0 -- verified byte-identical -- so tracking @v4 is safe.

• undici 7.29.0, closing all 12 open advisories (4 high)
• release-workflow hardening: tag names no longer reach a shell as source, and
  the published bundle is now verified against a rebuild before attestation
• @vercel/ncc 0.45.0 and dev-dependency bumps

v5.0.0
contains these same fixes plus a breaking change: commit subjects render as
literal text, so a merged pull request's subject can no longer inject links or
mentions into your release notes. That change also stops #123 autolinking
inside subjects, which is why it is not on the v4 line.

---

• 8b3d973 - 4.9.0
• ab3e266 - fix: carry the bump:workflow provenance fix onto the v4 line
• f6a78ba - release: prepare the v4 maintenance line
• 8becfce - fix(deps): bound the dependency overrides and clear the undici advisories (#476)
• f723555 - build(deps-dev): bump @vercel/ncc from 0.44.1 to 0.45.0 (#470)
• 88097f8 - build(deps-dev): bump eslint from 10.8.1 to 10.9.0 (#472)
• 430ccb9 - build(deps-dev): bump globals from 17.9.0 to 17.11.0 (#471)
• d40422b - build(deps): bump the codeql-action group with 3 updates (#469)
• ba35f7d - Verify release bundle before attestation (#474)
• 91ac6bb - Render changelog subjects as literal text (#475)
• c2ec39e - Keep release tag names out of shell source (#473)
• b28b10d - ci: let the stale workflow be run on demand (#467)
• d255efb - build(deps): bump actions/setup-node from 6.5.0 to 7.0.0 (#463)
• 20397cc - build(deps): bump actions/checkout from 6.0.2 to 7.0.1 (#450)
• 67da1d3 - build(deps): bump actions/stale from 10.2.0 to 11.0.0 (#462)