feat: add mobile chat view for live agent sessions

[karngyan]

Summary

• link running shell sessions to the freshest Claude, Codex, or Pi transcript in the same working directory, so this can ship ahead of the agent-hooks epic
• add a conversation-first mobile view with virtualized history, live daemon-pushed transcript pages, working and queued states, and a keyboard-safe composer that writes through the existing PTY
• render terminal prompts as tappable choices when they can be parsed, with a one-tap terminal escape hatch when they cannot
• add Chat / Terminal switching, mobile and desktop defaults, per-device preference persistence, Interrupt via Esc, and compact/clear shortcuts
• share the normalized transcript renderer between the history viewer and live chat

The interaction follows the useful shape from T3 Code's mobile client: conversation as the primary surface, approvals immediately above the composer, and the full terminal kept as an explicit escape hatch.

Verification

• go test ./...
• pnpm vitest run --maxWorkers=4 in web: 1,925 tests passed
• pnpm test in relay: 163 tests passed
• make lint
• pnpm run build in web

Closes #133

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