v0.1.0a15

mordred-hermes 0.1.0a15

Packaging-hygiene release on top of 0.1.0a14. No runtime code changed:
src/ is identical to a14 apart from the version string.

The published a14 sdist still shipped six dev-era PoC harnesses; a15
excludes them.

a14 sdist: install.sh, keyvault_offline_digest.py,
poc_outbound_roundtrip.py, poc_pre_gateway_dispatch.py,
poc_reply_encryption_regression.py,
poc_reply_key_failclosed.py,
poc_thread_reply_encryption.py, poc_wrap_live_adapters.py
a15 sdist: install.sh, keyvault_offline_digest.py

Changes

• Exclude scripts/poc_*.py from the sdist so published artifacts carry
  only the two scripts users need (#109)
• Tighten CI config and scripts hygiene; translate remaining Japanese
  comments in release.yml and docs/dev/CI.md to English (#109)
• Bump the GitHub Actions group: checkout v7.0.1, setup-python v7.0.0,
  upload-artifact v7.0.1, download-artifact v8.0.1, labeler v7.0.0,
  cache v6.1.0, github-script v9.0.0 (#108)
• Bump every pinned version surface to 0.1.0a15 (#110)