feat(flow-chat): redesign steering queue and composer editing

[GCWing]

Summary

• add a public ChatComposer queue anatomy using the new design system, with a fixed header, four visible message rows before scrolling, per-message image counts, secondary idle text, and hover/focus actions
• make queue rows display-only; the right-side Edit action restores the complete draft to ChatInput and removes the item only after restoration succeeds
• preserve text, contexts, image attachments, and large-paste substitutions across queueing, draining, persistence upgrades, and device-surface recovery
• make the Design Lab command-preview contract newline-safe on Windows

Validation

• pnpm run design-system:check
• pnpm run check:web
• pnpm run i18n:audit
• focused FlowChat queue, sender, draft, and orchestration tests: 48 passed
• targeted ESLint: 0 errors
• motion audit reviewed; only the existing PortForwardDialog inventory item remains

Remote scenarios

The automated MessageModule and pending-queue coverage exercised the local queue plus device-surface switch/requeue contracts. Manual Remote Control, Peer Device, Remote Workspace, and Detached Dispatch UI verification was not performed.

Visual verification

Per the FlowChat repository guidance, no browser automation or agent-driven UI interaction verification was run; final rendered comparison remains for human review.