Two new right-click-toggleable status bar items, mirroring the CLI/TUI
Pantheon status bar upgrades: prompt-cache hit rate ("87%") and rolling
output throughput ("42 t/s"). Both are hidden by default and enabled from
the bar's existing 'Show in status bar' context menu, like the context meter.
Renderer-only: the tui_gateway already emits cache_hit_pct and avg_tps in
every session.usage tick and message.complete payload, so the items ride
the same UsageStats the context meter reads — no new RPC, no polling.
Labels show a placeholder until the backend has data, never self-hide.
Teknium
3e63367175