[TheGreatAxios]

Summary

• packages/chat-ui/src/wire/* were already self-contained copies of the browser-safe @corbits/chat modules (no remaining @corbits/chat imports) except workbench-host-naming.ts, which is deleted outright — no host runs exist after the tenancy cutover.
• Deleted the chat features not carried into the mail cutover: reactions/pins were already gone from this surface; removed poll/form/question blocks and their response round-trip (block-responses.ts), the connect-github chat block and its onboarding-walkthrough plumbing, chat invites (invite-agent-dialog.tsx, composer mention pre-invite/"bring in" machinery), and slash commands (slash-commands.ts and the composer's / grammar, help popover, and /summarize macro).
• packages/chat-ui/src/blocks/registry.tsx now only routes approve, steps, metrics, stream, and connect-service block kinds.
• Trimmed packages/chat-ui/src/mentions.ts down to plain @mention autocomplete (kept activeMentionQuery, filterMentionCandidates, insertMention, mentionCandidatesFromParticipants); the "bring-in" invite-picker half is gone.
• apps/web/src/insights-stats.ts's purposeRunsForInsights no longer imports isWorkbenchHostDefinitionName (module deleted) — it's now an identity pass since no workbench-host runs exist post-cutover.
• Deleted apps/web/src/block-response-actions.ts (only consumer of the removed block-response wire) and its usage in chat-page.tsx.
• No package.json dependency changes were needed — the @corbits/chat / @corbits/commands / @corbits/agent-runtime / @corbits/turn-artifacts imports across chat-ui, settings-ui, notify, evals, and apps/web were already clean before this PR (a prior PR had done that half of the cutover); this PR's job was the wire-module ownership and not-carried-feature deletion.

Verification

• git grep -n "@corbits/chat\b\|@corbits/chat/\|@corbits/commands\|@corbits/agent-runtime\|@corbits/turn-artifacts" apps/web packages/chat-ui packages/settings-ui packages/notify packages/evals returns only README/comment prose (no live imports).
• bun run typecheck (repo-wide), bun run lint, bun run fmt:check all pass.
• bun test in packages/chat-ui, packages/settings-ui, apps/web all green (656 / 157 / 768 pass respectively).
• scripts/ci-jobs.test.ts has 3 pre-existing failures (CI job-list expectations) reproducible on origin/main before this change — unrelated to this PR, left as-is.
• packages/notify typecheck shows pre-existing vendor/intx stale-build (TS6305) errors unrelated to this change (vendor dist not rebuilt in this worktree).

Test plan

• bun run typecheck
• bun run lint
• bun run fmt:check
• bun test in chat-ui, settings-ui, apps/web

[linear-code]

CL-8175