docs: rephrase the vale warnings that have a better wording

Words the alex and Microsoft styles flag where a plainer one reads as well:
disabled/special/invalid as a state, primitive, trap, hang, several, click,
first-person FAQ questions, hyphenated adverb pairs. Left as they are: Let's
Encrypt, quoted UI labels and phrases, the generated forge CLI reference, and
the middle-click gesture.

docs/web-ui/agent.md

@@ -128,7 +128,7 @@ and scrolls behind the fixed header + footer.
   `.agent-main`**, not in `log.parentElement = .terminal-wrap`:
   `.terminal-wrap` applies `backdrop-filter: blur` for the frost
   effect, which creates a CSS stacking context — anchoring the
-  pill inside that context would trap its `z-index` below the
+  pill inside that context would confine its `z-index` below the
   fixed composer in the root stacking context, and it'd never
   float. `.agent-main` has no backdrop-filter (no stacking-context
   creators), so the pill's `z-index` reaches the root and properly
@@ -259,8 +259,8 @@ Unknown `/foo` shows an error row instead of being silently sent.
 ## Per-agent endpoints
 
 Successful POSTs return 200 (no 303 redirects). Error responses
-use semantic status codes: **400** for missing/invalid input
-(`body` required, unknown model name, invalid effort level),
+use semantic status codes: **400** for missing/malformed input
+(`body` required, unknown model name, unrecognised effort level),
 **409** for retryable state conflicts (turn in flight when
 `/compact` fires), **500** only for genuine server/transport
 failures. The matching
@@ -358,7 +358,7 @@ shaped).
   dimensions; enabled once the server advertises the
   `ExtendedDesktopSize` pseudo-encoding (`-308` rect in the header).
   Fit-mode state persists in `localStorage` (`screen-fit`); default
-  is on. `sendPointer` rescales pointer coordinates so clicks
+  is on. `sendPointer` rescales pointer coordinates so presses
   land on the right pixel regardless of CSS scale.
 - `GET /screen/ws` — raw RFB byte relay: proxies WebSocket
   frames to the weston VNC server at `127.0.0.1:<vnc_port>`.