fix(mobile): add close controls to tablet files and terminal

[juliusmarminge]

On iPad, the persistent Files pane has no local close control, and the split-view Terminal screen hides the navigation back button. Add explicit close buttons so users can dismiss Files or return from Terminal to their thread. This addresses items 7 and 8 in #10985.

Files uses the existing auxiliary-pane visibility action. Terminal goes back when possible and replaces an initial terminal route with its thread when there is no history. The Android header uses the same terminal handler; the iPhone native back-button layout is unchanged. Closing Terminal keeps the shell alive.

Verified on an iPad Pro 13-inch simulator running iPadOS 27: open/close Files, open an existing shell, close Terminal with the keyboard visible, and return to the conversation. Before/after captures use the actual base/head UI source with the same fixture and viewport. The integrated phone compact/expanded composer and keyboard-up send checks passed. Mobile typecheck, targeted lint, and 45 layout/adaptive-navigation/voice-presentation tests passed. Android runtime verification has not been performed.

This PR is independent of the composer animation fix in #11114. It changes only navigation controls.

Files before	Files after

Terminal before	Terminal after

Closing Files, opening an existing terminal, and returning to the thread, at normal speed:

Implemented and verified with GPT-6 in Codex.

Summary by CodeRabbit

• New Features
  • Added controls to close the file navigator pane on iOS and other mobile layouts.
  • Added consistent terminal closing behavior, including an iOS split-view close button and Android header navigation.
  • Terminal closing now returns to the previous screen when possible, or the thread screen otherwise.

[macroscopeapp]

Approvability

Verdict: Approved at f3a3cc1

Macroscope's review found this PR approvable — The changes add localized close controls to existing tablet file and terminal surfaces, reusing established pane visibility and navigation behavior. Runtime impact is limited to dismissing those surfaces or returning to the thread, with no schema, security, billing, deployment, or default-setting changes.

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[coderabbitai]

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ℹ️ Recent review info

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Run ID: 683d5d8e-8b26-42e8-ae77-d8025f341378

📥 Commits

Reviewing files that changed from the base of the PR and between d2eeacd and f3a3cc1.

📒 Files selected for processing (2)

• apps/mobile/src/features/files/thread-file-navigator-pane.tsx
• apps/mobile/src/features/terminal/ThreadTerminalRouteScreen.tsx

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📝 Walkthrough

Walkthrough

The mobile file navigator now closes through adaptive workspace layout controls. The terminal screen now uses shared close navigation for Android back handling and an iOS split-view close button.

Changes

Mobile workspace navigation

Layer / File(s)	Summary
File navigator close controls apps/mobile/src/features/files/thread-file-navigator-pane.tsx	The file navigator uses toggleAuxiliaryPane for the iOS “Close files” header button and the non-iOS close button.
Terminal close navigation apps/mobile/src/features/terminal/ThreadTerminalRouteScreen.tsx	Terminal close handling pops when possible and replaces the route with the thread screen otherwise. Android back handling and the iOS split-view close button use this callback.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to f3a3c

The change adds mobile close controls for Files and Terminal while preserving terminal sessions. No merge-blocking product or runtime risk is currently evident.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the Files and Terminal changes, the reason for the changes, UI evidence, verification results, and the unperformed Android runtime verification. It omits the template …
Title check	✅ Passed	The title clearly and concisely identifies the primary change: adding close controls for tablet Files and Terminal views on mobile.
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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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.6 KiB	13.6 KiB	+18 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.0 KiB	7.1 KiB	+9 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.6 KiB	6.6 KiB	+9 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.1 KiB	57.1 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	−34 B (−0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+7 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.5 KiB	−41 B (−0.6%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.8 KiB	57.8 KiB	−44 B (−0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	8	−1 (−11.1%)	21	✅

Baseline: d2eeacd · PR result: f3a3cc1 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.