chore(v0.5): release readiness tracker

[jackby03]

v0.5 Release Tracker — Observability & Continuous Compliance

P0 — Must Ship

• feat(watch): hardbox watch — continuous audit daemon #134 hardbox watch — continuous audit daemon
• feat(alerts): webhook and alerting integration #135 Webhook / alerting — Slack and HTTP webhooks
• feat(serve): fleet overview in hardbox serve dashboard #136 Fleet overview in hardbox serve

P1 — Should Ship

• feat(profiles): profile inheritance via extends key #137 Profile inheritance via extends key
• feat(serve): compliance score trend history #138 Compliance score trend history in serve

P2 — Nice to Have

• feat(reporting): SARIF export format #139 SARIF export format

Release checklist

• All P0 issues closed
• CHANGELOG.md [0.5.0] section updated with final entries
• docs/WATCH.md written and linked from README
• docs/SERVE.md updated (fleet overview + trend history)
• quality-gates.yaml passes on main
• release-smoke.yaml passes on the release tag
• GoReleaser tag v0.5.0 published