[TheGreatAxios]

Summary

• Bumps every github:corbitsdev/corbits-mailbox pin to e85b81e4 (1.0.0, breaking) across apps/hub, packages/chat, packages/inbox.
• apps/hub/src/index.ts: the mountMailbox call is rewritten for the new resolvePrincipal/senderAddressFor/deliver mount contract — senderAddressFor derives <principalId>@<tenant domain>, and deliver reuses the same dual-write lookups.persistMail (createMailboxPersist) every outbound agent frame already goes through, so a human's POST /me/inbox/send and an agent's own outbound mail share one delivery path (live run via the vendored session/mail routing, human recipients via the mailbox dual-write). apps/hub/src/mailbox-persist.ts drops the retired resolveRefs seam (refs no longer exists on the package).
• The @corbits/inbox product-inbox routes (createInboxRoutes, mounted at ${TENANT_PREFIX}/inbox) are deleted (CL-8209): they sat entirely on removed @corbits/mailbox APIs (listUserMailbox, refs, classification), and no web surface reads them any more — /inbox in the web app only bounces old links home (CL-6151).
• packages/chat/src/mailbox-fanout.ts: writes one writeMailboxMessage append per recipient (outbound → Sent, inbound → INBOX) instead of the retired batch writeMailboxMessages transaction — the native store has no multi-row batch. refs stamping is gone.
• packages/chat-ui/src/mailbox-timeline.ts (the single browser-side mailbox adapter) now reads GET /me/inbox/threads instead of the retired /me/threads + refs API. Since a workbench is a plain tenant (CL-8083), a tenant's own mailbox already is that one room's mail, so there's no per-room ref filter to apply any more.
• packages/inbox is trimmed to just the @corbits/notify → @corbits/mailbox delivery adapter (delivery.ts, rewritten against deliverInboxItems's new no-refs InboxItem shape) and its own migration ledger (migrations.ts). Deleted: routes.ts, thread-client.ts, client.ts, vocabulary.ts, group.ts, project.ts, bulk.ts, bulk-run.ts, cursor.ts, walk.ts, and their tests — all built on removed @corbits/mailbox exports.

What's left on the old chat send path

The composer's send action (useOptimisticSends → sendMessage in packages/chat-ui/src/api.ts) still posts through the existing chat message route, not POST /me/inbox/send directly — that route's server-side fan-out (writeChatMailboxFanout) already lands the mailbox copy via the rewritten mailbox-fanout.ts above. Wiring the composer to call /me/inbox/send directly (with inReplyTo set to the thread root Message-ID) is follow-up work, not done here.

Test plan

• bun run typecheck — green
• bun run lint / bun run fmt:check — green
• bun run check:structural — green
• bun test — green except 7 packages with pre-existing failures unrelated to this change (@intx/hub-agent, @corbits/workbench-digest-workflow, @corbits/workflows, @corbits/webhook-triggers, @workbench/onboarding, @corbits/chat's platform-adapter.test.ts launch/deploy fixtures, @corbits/chat-ui's act()/happy-dom teardown flakiness) — none reference mailbox/inbox and none touch files this PR changes
• DB-gated mailbox suites (packages/inbox/test/delivery.test.ts, apps/hub/test/mailbox-persist.test.ts, apps/hub/test/notify-delivery.test.ts) were rewritten for the new API but not run against live Postgres in this session (port 5432 was already bound by another worktree's compose); CI's db-suites/e2e-suite jobs will exercise them

[linear-code]

CL-8174

CL-8209