Trim negative-space comments per mara's review

Don't state what a function/module doesn't do and where that
happens instead — just describe what it does. Cut the "not
something this function decides" / "not affected by this" /
"not a placeholder for a later commit" asides from the doc
comments touched in the last two commits.

frontend/packages/agent/src/hooks/useAgentState.ts

@@ -1,13 +1,5 @@
-// useAgentState — polls `GET /api/state` and exposes the latest
-// snapshot + loading/error status. Mirrors app.js's old `refreshState`
-// data fetch, not its exact re-poll cadence: the old page re-polled on a
-// timer only while a login was in flight, and otherwise waited for an
-// SSE `turn_end` event to trigger one-shot refreshes. That SSE-triggered
-// model is permanently off the table now — the terminal stream's `kind`
-// tag (what let a client single out a turn-boundary event) is gone by
-// design, see `useLiveStream.ts`'s module doc — so this hook's flat 4s
-// interval is the only refresh path, not a placeholder for a later
-// commit.
+// useAgentState — polls `GET /api/state` every 4s and exposes the latest
+// snapshot + loading/error status.
 import { useEffect, useRef, useState } from 'preact/hooks';
 import type { AgentState } from '../types.js';