Add a live activity log to the dashboard

[iTerminate]

Summary

• DashboardScreen becomes a third LogbookController host alongside HACLI's docked panel and GraphPreviewScreen's: a opens a docked activity log defaulting to the whole dashboard's entities, v narrows the scope (dashboard/devices/cursor slot/cursor's device), f maximizes it, and it follows the grid cursor as it moves.
• Unlike GraphPreviewScreen, the dashboard log is live, so LogbookController now lets the singleton WS logbook subscription hand off between two simultaneously live-capable, visible sessions (the main screen's panel stays -visible behind a pushed dashboard) — it follows whichever screen is on top and resyncs on close/screen transitions.
• Docked vs. maximized paging keys differ from the other two hosts because the dashboard grid genuinely needs ←/→ for cursor movement: [/] page while docked, ←/→ take over once maximized (the grid is hidden then).

Test plan

• pytest (full suite, 1297 tests) passes
• uv run pyright / uv run ruff check . clean
• New tests/test_dashboard_activity_log.py (11 tests) covers open/close, edit-mode fallthrough to the slot popup, scope popup, maximize+paging, docked paging, the escape ladder, live stream append, subscription handoff with the main screen, and session cleanup on leaving the dashboard
• New unit tests for DashboardController.dashboard_entity_ids and for LogbookController's two-live-host handoff / torn-down-host tolerance