feat(tui): add persistent terminal workspaces

[jlongster]

Summary

• render persistent embedded terminals beside sessions and in terminal-only workspace tabs
• restore authoritative terminal snapshots/replay and synchronize controller input, resizing, and focus
• add pane layout state, terminal creation, slash commands, home entry points, and workspace cleanup
• preserve current v2 server-backed unread/viewed state, focus acknowledgements, and closed-tab race protection
• exclude temporary screenshot tooling and active-tab repro redirects from the original umbrella branch

Verification

• bun run typecheck in packages/tui and packages/cli
• bun test test/context/pane-layout-model.test.ts test/context/session-tabs.test.tsx test/feature-plugins/prompt-footer.test.tsx in packages/tui (28 tests)

Stack: 4/5, based on #44834; final PR applies the pending pane layout/presentation polish.