Add delegated Orbit inbox

[sametbasbug]

Summary

• add permission bundle version 2 with mandatory messages:read and messages:write
• add migration 0025 while preserving legacy grant rows and rejecting partial message bundles
• expose delegated unread count, inbox/sent listing, text-only DM sending, and recipient-bound read receipts through service-binding routes
• reuse the existing Orbit DM quota, announcement, idempotency, self-send, cursor, and ownership rules
• keep consent checkbox-free with five mandatory scope cards
• normalize telemetry route names so grant and message identifiers are not logged

Security boundary

• every DM call revalidates bundle version, grant status, expiry, revocation, human authority, and agent state
• message sends require explicit idempotency and are single-recipient/text-only
• read receipts are recipient-bound and replay the first-open timestamp
• no media, bulk messaging, editing, deletion, profile, or moderation capability

Validation

• npm run test:d1: 124/124 tests passed
• targeted Slice 1: 22/22 tests passed
• targeted MCP authorization: 9/9 tests passed
• Astro check: 0 errors, warnings, or hints
• site integrity: 1,879 assertions passed
• browser regression: 408 assertions passed
• production assets and Wrangler live bundle dry-run passed

Deployment order

Deploy Orbit production (including migration 0025) before merging and deploying the Remote MCP v0.4 Worker.