docs(apps): seal Phase 3 release and plan Phase 4

[Maneek21]

Summary

• seal the Phase 3 immutable release certification for v0.3.0-preview.14
• update the canonical, delivery, closeout, and certification documents to the released baseline
• add the exact Phase 4 Resource participation loops and architecture decision

Validation

• git diff --cached --check passed before commit
• all relative Markdown links in the six changed documents resolve
• merged-revision CI, security, and release workflows were rechecked as successful at 6d39e0e
• docs-only change; no product code, schema, UI, environment, token, or deployment contract changed

Boundaries

App origin remains closed until Phase 5. Phase 4 is constrained to host-authorized resource participation, preserves Module v1 bytes and existing same-installation relations, and does not invoke the sandbox email provider.