fix(mobile): keep composer within folded screen after resume

[PixPMusic]

Leaving a thread unfolded, backgrounding the Android app, then returning on the cover display can leave the composer at its old split-pane width. The header and transcript resize correctly, but the input extends beyond the screen and Send disappears.

Give the compact composer an explicit 100% parent-relative width instead of clearing its animated width. Split layouts keep their existing live pane width, with the dock anchored from the left. The editor stays mounted, preserving its draft and focus.

Before / After

Android 17 Pixel 9 Pro Fold emulator, identical native client, dark theme, 100% system text, and disposable showcase data. Both captures follow unfolded thread → Home → fold → resume.

Before: composer overflows, Send missing	After: composer and Send fit

Before resume recording · After resume recording

Screenshots are 1080 × 2424. Recordings show the cover display returning to the app after folding in the background. Evidence is hosted on the fork; no proof assets are committed.

Verification

• Reproduced the missing Send control on base f5ef0ddb90; the same sequence passes with the fix.
• Verified both resize directions, sidebar hide/show, and file-inspector open/close. Send remains inside the available pane.
• Backgrounded with the keyboard open, folded, and resumed: draft text and Send survive; keyboard dismissal keeps both correct.
• ./node_modules/.bin/vp run --filter @t3tools/mobile typecheck passes. Scoped lint passes with existing warnings; scoped formatting and git diff --check pass.
• Shared mobile dock only. Android verified; iOS runtime behavior was not exercised. No web, desktop, provider, contract, or connection-protocol changes.

Model: GPT-6 (variant not exposed) | Harness: Codex in T3 Code

Summary by CodeRabbit

• Bug Fixes
  • Corrected the composer dock’s width and alignment in split and full-width layouts, including when workspace sizing is unavailable.

[macroscopeapp]

Approvability

Verdict: Approved at 5bf358a

Macroscope's review found this PR approvable — This is a narrowly scoped mobile layout bug fix that explicitly keeps the existing composer within its current parent width across compact and split layouts. It changes no APIs, defaults, infrastructure, security-sensitive code, or static-analysis configuration.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: pingdotgg/t3code/.coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: 466651f2-9488-4504-8844-c6f2f66cddae

📥 Commits

Reviewing files that changed from the base of the PR and between 5bf358a and adb7ccb.

📒 Files selected for processing (1)

• apps/mobile/src/features/threads/ThreadDetailScreen.tsx

Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

ThreadDetailScreen now sets an explicit composer width in both layout branches. The sticky host no longer sets right: 0.

Changes

Thread composer layout

Layer / File(s)	Summary
Composer width and positioning apps/mobile/src/features/threads/ThreadDetailScreen.tsx	The split-layout style sets the width to workspaceContentWidth.value; the other branch sets it to "100%". The sticky-host Animated.View no longer sets right: 0.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to adb7c

The explicit composer sizing follows the visible workspace through pane and inspector changes. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the mobile composer fix for folded-screen resume behavior. It is concise and directly matches the main change.
Description check	✅ Passed	The description explains the problem, implementation, UI impact, evidence, and verification results. It omits the template's explicit Checklist section, but the required checklist information is subst…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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