[TheGreatAxios]

Closes CL-12083

What changed

A project with no model provider connected showed an error banner in place of the composer. The composer now stays, disabled, with the placeholder "Enable AI to start the conversation" and a highlighted Enable AI button in place of Send; the mic and attach controls are hidden. Enable AI opens the model setup provider tiles in a dialog, so connecting never leaves the project; once connected, the coordinator starts.

Only model_provider_missing gets this. model_profile_required keeps the existing banner with Open Settings and Retry, since connecting another provider cannot settle a profile choice.

• model-setup.tsx: the tiles move into ProviderTiles, shared by ModelSetup and the new EnableAiDialog.
• workspace/index.tsx: modelRefusal returns the refusal code with its message, and the composer branches on it.
• config.ts: action.enableAi, conversation.enableAiFirst.

How it was verified

• bun run test: 218 passed, 0 failed.
• bun run lint, bun run format:check, bun run typecheck: passed.
• In the app with no provider: the composer shows Enable AI and the placeholder, the dialog opens, and an API-key tile opens the key prompt over it. A real connection was not exercised.

[linear-code]

CL-12083

[TheGreatAxios]

Self-Review Summary

Reviewed the branch against origin/main with /code-review. One blocking issue was found and fixed before pushing.

Files Reviewed

• apps/web/src/pages/model-setup.tsx: moves the tiles into ProviderTiles and adds the EnableAiDialog wrapper. No behaviour change to ModelSetup.
• apps/web/src/pages/workspace/index.tsx: branches the composer and banner on the refusal code.
• apps/web/src/config.ts, apps/web/src/App.tsx: wording, prop wiring.

Issues Found and Resolved

• Enable AI showed for model_profile_required, which a new provider cannot fix, and the Open Settings path had been removed (dead end). Now gated on model_provider_missing; the profile cases keep the banner.
• The locked composer did not say why: placeholder added.
• Mic and attach stayed live on the locked composer: hidden.
• Unused enable-ai-dialog class: removed.

Known, not addressed

• A provider connected outside the dialog only takes effect after reopening the project.
• Closing the dialog mid subscription login drops the in-flight guard, so a second login can start.
• The web refusal set omits model_profile_custom (this was already the case).
• No automated test covers the new flow.

[corbits-triage]

Triage: Pass

No changes needed from you. A maintainer will review this pull request.

[corbits-triage]

No defects reported.