feat(mobile): add composer attachment menu with video support

[rynfar]

Last of the mobile batch, closing DEF-10. Adopted from upstream pingdotgg/t3code#8843 (e3dcc1615) plus its follow-up f9137a0c8.

Stacked on #233 — #8843 lands after #8614 upstream, so this branches from the voice-input work. Merge #233 first.

What it does

The + control opens a native menu anchored beside it with Photo Library and Choose Files, replacing the Alert sheet. Videos are accepted against the server's file upload limit. An empty composer also shows the interrupt button while the agent works; adding text or an attachment swaps it for send.

The restructure, one last time

Twelve of the thirteen ThreadComposer conflicts were #8793's toolbar restructure arriving as context yet again — declined, as in #223, #231 and #233. The genuine content is ComposerAttachmentButton and the showStopAction change, both placed into Pylon's structure: the button lives inside Pylon's toolbar scroller rather than upstream's fixed left group.

Worth noting the split is holding — the ComposerSurface hunks adopted in #233 did not conflict this time.

Two silent drops a clean typecheck would not have caught

Both arrived through non-conflicting hunks, which is the failure mode this batch keeps producing:

• ComposerToolbarButton was removed from the import list. Upstream's restructure replaced every call site, so they dropped the import. Pylon still has eleven call sites. This one did surface as a type error only because the identifier was referenced; had the import merely gone unused it would have passed silently.
• IconPhoto arrived in the symbol map with no import behind it. Upstream adds it via a per-icon deep import (@tabler/icons-react-native/IconPhoto) while Pylon uses the barrel, so the map entry merged cleanly and the import did not. Re-applied in Pylon's style.

I also broke AppSymbol.tsx mid-resolution with an over-eager union script and restored it from HEAD rather than patching over the damage.

Verification

Typecheck clean, lint clean, 1062 tests passing. The follow-up commit f9137a0c8 applies line-for-line identical to upstream.

Not yet run on a simulator. The native menu is the thing to check — it is a @react-native-menu/menu surface, so it needs a device or simulator pass rather than unit coverage.

Pylon features intact: scroller 3, ControlPillMenu 13, QuickQuestionTrigger 2, ContextWindowIndicator 3, ComposerToolbarButton 11.

Reviewed and integrated with Claude Opus 5 in Claude Code.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}

[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	13.7 KiB	13.5 KiB	−211 B (−1.5%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	+6 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.6 KiB	−217 B (−3.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.7 KiB	57.1 KiB	−1.5 KiB (−2.6%)	66.4 KiB	✅
Codex	Live turn messages	11	9	−2 (−18.2%)	21	✅
Claude	Total thread wire	13.5 KiB	13.6 KiB	+41 B (+0.3%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	+2 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.6 KiB	+39 B (+0.6%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.0 KiB	58.1 KiB	+44 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	10	+1 (+11.1%)	21	✅

Baseline: 81bdef6 · PR result: e771165 · 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: 109.5 KiB
• Claude decoded thread snapshot: 110.2 KiB

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