refactor(core): own composer model policy

[richardsolomou]

Problem

Mobile's two composers duplicated desktop's model availability and reasoning compatibility decisions. The picker and button presentation is platform-specific, but those policy decisions are not.

Depends on #3635
Refs #2416

Changes

I moved restricted-model selection and reasoning compatibility into core and switched mobile to those policies. Mobile keeps its picker mapping, labels, and native controls.

How did you test this?

• Ran 2,576 core tests, including composer model policy coverage.
• Ran 413 mobile tests.
• Ran core/UI, desktop, and web typechecks, Biome, and the host-boundary check.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

---

Created with PostHog Code

[github-actions]

React Doctor found 10 issues in 2 files · 10 warnings.

10 warnings

src/app/task/index.tsx

• ⚠️ src/app/task/index.tsx:222 Event logic handled in an effect no-event-handler
• ⚠️ src/app/task/index.tsx:223 Event logic handled in an effect no-event-handler
• ⚠️ src/app/task/index.tsx:225 Derived value copied into state no-derived-state
• ⚠️ src/app/task/index.tsx:226 Derived value copied into state no-derived-state

src/features/tasks/composer/TaskChatComposer.tsx

• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:213 Event logic handled in an effect no-event-handler
• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:214 Event logic handled in an effect no-event-handler
• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:216 Data passed to parent via effect no-pass-data-to-parent
• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:216 Parent kept in sync with a callback effect no-prop-callback-in-effect
• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:217 Data passed to parent via effect no-pass-data-to-parent
• ⚠️ src/features/tasks/composer/TaskChatComposer.tsx:217 Parent kept in sync with a callback effect no-prop-callback-in-effect

_{Reviewed by React Doctor for commit 44c040d.}

[richardsolomou]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(mobile): add Codex task parity #3654
• refactor(mobile): finalize portability boundary #3642
• refactor(mobile): reuse inbox semantics #3641
• refactor(mobile): reuse session display semantics #3640
• refactor(core): own composer model policy #3637 👈 (View in Graphite)
• refactor(mobile): reuse transport and permission policies #3635
• refactor(mobile): reuse inbox transport #3634
• refactor(mobile): reuse repository aggregation #3633
• refactor(mobile): finish shared cloud task adoption #3608
• refactor(mobile): reuse the cloud task engine #3624
• refactor(mobile): reuse core task policies #3623
• refactor(mobile): reuse the task API client #3622
• refactor(mobile): reuse task contracts and model policy #3616
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
apps/mobile/src/features/tasks/composer/options.ts:62-64
**Recording stop becomes task stop**

When a remote user message starts an agent turn while the local user is recording, `canStop` takes precedence over `isRecording`, so the unchanged stop control cancels the agent turn instead of stopping voice capture, leaving the recording active and potentially losing the user's speech.

### Issue 2 of 2
apps/mobile/src/features/tasks/composer/TaskChatComposer.tsx:500-508
**Unchanged reasoning triggers side effects**

Selecting a model that supports the current reasoning effort still invokes `onReasoningChange`, causing a redundant `set_config_option` cloud command and unnecessary persisted Zustand updates.

_{Reviews (1): Last reviewed commit: "Merge posthog-code/share-mobile-mcp-skil..." | Re-trigger Greptile}