chore(release): prepare v0.10.0

[zikolach]

Summary

• add the v0.10.0 changelog entries for remote new-session handoff (feat(relay): hand off new sessions across messengers #84) and autonomous broker route recovery (fix(broker): self-heal route registration #85)
• sync completed OpenSpec deltas into the main specifications
• archive remote-new-session-handoff and self-heal-broker-route-registration
• bump package metadata to 0.10.0

Validation

• npm run typecheck
• npm test (808 passed, 2 skipped)
• openspec validate --all --strict (28 passed)
• npm pack --dry-run
• git diff --check