fix(control-ui): keep context usage fresh (#71297)

Patch live session usage metadata into the Control UI session list, coalesce overlapping refreshes, and add a compact action when fresh context usage is high.

Keep session refresh loading separate from session mutation ownership so background refreshes cannot re-enable mutation UI or overwrite delete/restore state mid-flight.

Co-authored-by: Val Alexander <68980965+BunsDev@users.noreply.github.com>

docs/web/control-ui.md

@@ -156,6 +156,10 @@ Cron jobs panel notes:
 - `chat.history` also strips display-only inline directive tags from visible assistant text (for example `[[reply_to_*]]` and `[[audio_as_voice]]`), plain-text tool-call XML payloads (including `<tool_call>...</tool_call>`, `<function_call>...</function_call>`, `<tool_calls>...</tool_calls>`, `<function_calls>...</function_calls>`, and truncated tool-call blocks), and leaked ASCII/full-width model control tokens, and omits assistant entries whose whole visible text is only the exact silent token `NO_REPLY` / `no_reply`.
 - `chat.inject` appends an assistant note to the session transcript and broadcasts a `chat` event for UI-only updates (no agent run, no channel delivery).
 - The chat header model and thinking pickers patch the active session immediately through `sessions.patch`; they are persistent session overrides, not one-turn-only send options.
+- When fresh Gateway session usage reports show high context pressure, the chat
+  composer area shows a context notice and, at recommended compaction levels, a
+  compact button that runs the normal session compaction path. Stale token
+  snapshots are hidden until the Gateway reports fresh usage again.
 - Talk mode uses a registered realtime voice provider that supports browser
   WebRTC sessions. Configure OpenAI with `talk.provider: "openai"` plus
   `talk.providers.openai.apiKey`, or reuse the Voice Call realtime provider