chore: address Copilot review round 1 (#2192)

- `useEmaIdpLoginState`: the effect-triggered `refresh()` was discarded with
  `void`, but it does not own its failures — `getEmaIdpLoginState` awaits
  `storage.getIdpSession`, which rejects when the backend is unreachable.
  Terminate with `.catch()` and leave `loginState` untouched, as `logout`
  already does. Covered by a new test that also asserts no unhandled
  rejection escapes.
- Correct the history: the plugin was *client-local*, declared by both
  `clients/web` and `clients/tui`. The root could reach neither, since Node
  resolution walks up rather than down — that, not web-exclusivity, is why
  `core/react/` went unlinted.
- Correct the enforcement claim: `clients/tui` registers the plugin but
  deliberately enables only `rules-of-hooks` and `exhaustive-deps`, so
  `set-state-in-effect` and `refs` hold for `clients/web` and `core/react/`
  only. Says so in AGENTS.md and in the Copilot mirror, which would
  otherwise have reviewers cite rules the TUI gate does not run.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013hzwzS8UvBsr4yZm7o7sev
Signed-off-by: cliffhall <cliff@futurescale.com>

.github/copilot-instructions.md

@@ -51,7 +51,7 @@ const CardContent = Group.withProps({
 
 ### State and effects
 
-- **Never reset or re-sync local state from a prop inside a `useEffect`.** `useEffect(() => setX(prop), [prop])` paints the stale value first and renders twice; it is an error under `react-hooks/set-state-in-effect` — enforced in `clients/web`, `clients/tui`, and `core/react/**` (#2192). The same rule set forbids writing a ref during render (`react-hooks/refs`): sync a "latest value" ref in an effect instead.
+- **Never reset or re-sync local state from a prop inside a `useEffect`.** `useEffect(() => setX(prop), [prop])` paints the stale value first and renders twice; it is an error under `react-hooks/set-state-in-effect` — enforced in `clients/web` and, since #2192, in `core/react/**`. The same rule set forbids writing a ref during render (`react-hooks/refs`): sync a "latest value" ref in an effect instead. `clients/tui` is the exception — it enables only `rules-of-hooks` and `exhaustive-deps`, so do not cite these two against TUI code.
 - Use **`useValueChange(value, onChange)`** (`src/hooks/useValueChange.ts`) — React's documented "adjusting state during render" pattern. It does not fire on the first render; seed the state with `useState`. The comparison is `Object.is`, so pass a **referentially stable** value — a primitive key (id/name/URI) or a memoized one, never a fresh object literal.
 - The `onChange` runs **during render**, so it must be pure — `setState` and nothing else. No fetches, DOM writes, logging, ref mutation, or parent callbacks; a render can be replayed or abandoned.
 - Effects remain correct for real external-system synchronization (DOM measurement, rAF, subscriptions, timers).