feat(mobile): refine composer and session interface

[eivindjonassen]

Changes

• Match OpenCode's resolved terminal system theme across the mobile interface.
• Align list activity indicators, remove redundant Working and Succeeded labels, and use a compact in-session activity row.
• Move new-session creation to a compose icon in the header and remove duplicate connection controls from the list.
• Keep recent transcript output visible above the keyboard while preserving manual scroll position.
• Make the composer compact and use native multiline sizing. Fixed-height sizing waited on iOS Fabric layout-driven content-size events, leaving wrapped lines hidden.

Verification

• pnpm check passed, including iOS and Android Hermes exports.
• Expo Doctor passed all 18 checks.
• Public-tree and secret scans passed.
• Native fingerprints matched installed runtime 0.1.4 before direct preview OTA publication.
• User confirmed the multiline correction on the physical iPhone; recorded in docs/COMPATIBILITY.md.

These changes are already available through the directly published preview OTA.