docs: document model/context-window config, dynamic watermarks, rate-limit scoping

docs/web-ui.md

@@ -382,7 +382,9 @@ Layout, top to bottom:
     (input + cache_read + cache_write of the most recent
     model call in the just-ended turn). This is the **actual
     context window utilisation** — the number to watch when
-    deciding whether to compact.
+    deciding whether to compact. When `context_window_tokens`
+    is available from `/api/state`, the badge tooltip shows the
+    percentage of window used.
   - Cost badge: `cost · 1.3M` — cumulative tokens billed
     across **every inference** in the last turn (sum of all
     per-call prompts). Tool-heavy turns rebill the cached
@@ -407,7 +409,10 @@ Layout, top to bottom:
   Polling: `/api/state` is fetched **once** on cold load, and
   again while `status === 'needs_login_in_progress'` (login
   session output isn't event-shaped yet). Every other badge
-  updates from SSE; no periodic refresh timer runs.
+  updates from SSE; no periodic refresh timer runs. Snapshot
+  includes `context_window_tokens` (effective window size for
+  the agent's current model, from `events::context_window_tokens`)
+  used to compute percentage-of-window in the ctx badge tooltip.
 - Inbox `<details>` block (collapsed): `inbox · N` — last 30
   messages addressed to this agent, fetched via
   `AgentRequest::Recent { limit: 30 }`. Reply messages (those