chore: prepare v0.13.4 release

[yoloyash]

Summary

• update the default OvertChat app image in compose.yml from 0.13.3 to 0.13.4

Validation

The release candidate on the parent main commit passed:

• Host Connector build
• full monorepo validation
• browser E2E smoke suite
• focused queue, steering, reconnect, and canonical timeline coverage from fix(agents): stabilize queue, steer, and timeline ordering #153

The release bump also passes docker compose config --quiet.

Upgrade notes

• Host Connector 0.2.0 is required; Connector 0.1.0 is intentionally incompatible.
• Reinstall the connector after upgrading the server.
• No database migration is required.
• Agent Connections remains Beta.