Align iOS remote conversation UX with HarmonyOS

[wgqqqqq]

The iOS remote-control surface visibly diverged from the HarmonyOS reference in pairing, conversation rendering, composer behavior, navigation hierarchy, settings, and file preview controls. Short user messages also expanded into a fixed-width card, while assistant failure state was lost before reaching the native UI.

This change aligns the iOS experience with the HarmonyOS native implementation:

• renders pairing as an inline scanner with the same hierarchy, viewfinder treatment, manual fallback, pause/resume behavior, and off-main-thread QR processing;
• adds adaptive Markdown tables and task-list checkboxes;
• carries assistant turn status and errors through protocol, persistence, presentation, and the iOS failure/retry UI;
• makes user bubbles hug short content while retaining the shared width cap and line height, with pending/retry state outside the bubble;
• matches the HarmonyOS composer action policy and geometry, including mid-run draft preservation, send/stop/voice states, the supplemental microphone, border, and circular primary action;
• aligns conversation header controls, sidebar ordering and footer sizing, and removes the extra iOS-only sidebar action;
• aligns settings information architecture with current account, active remote control, language, default model, account devices, about, and sign-out sections;
• aligns remote file preview navigation and adds refresh beside download;
• updates shared modal headers and deterministic design-gallery fixtures for visual comparison.

Validation:

• iPhone 16 Pro simulator builds and compact light/dark visual captures;
• side-by-side iOS simulator and HarmonyOS foldable-emulator review for conversation, sidebar, settings, pairing, and file preview;
• read-only real-device account/workspace navigation through XCUITest;
• unsigned generic iOS device build;
• iOS focused pure Swift tests;
• shared KMP JVM and Android host tests for protocol/domain/feature changes;
• pnpm run mobile:ui:check;
• pnpm run mobile:architecture;
• git diff --check.

Remote-control presentation was exercised with deterministic connected-session fixtures on iOS simulators, the HarmonyOS foldable emulator, and a real iPhone account/workspace navigation path. This PR does not change remote-workspace execution, Peer Device Mode, or Detached Dispatch behavior.