fix(custom-model): address second pre-merge review (Ark0N)

Blocker: .center-status-banner never actually disappears.

- Add `.center-status-banner[hidden] { display: none; }`, same trap as
  `.home-sessions[hidden]`: the author-level `display: flex` beat the
  UA `[hidden]` rule, so `dismiss()` set `el.hidden = true` and the
  card stayed laid out at `opacity: 0` with its text/cancel/close
  children still `pointer-events: auto` -- an invisible 442x67 click
  blocker dead centre over the terminal until the page reloaded.
- Added a regression test pinning the CSS rule, and documented the
  banner (10001) and the swap-confirm/context-warning modals (10010)
  in CLAUDE.md's Z-index layers list.

Stale wording pointed at the reverted sticky-toast default:

- .changeset/run-menu-custom-model-picker.md, CLAUDE.md, and the
  `.toast-message` comment in styles.css all still said "toasts
  default to sticky" after 1f32128c put the flat 3s default back.
  Reworded all three to describe the actual behaviour: one call site
  passes an explicit `duration: 0`.

Smaller items from the same review:

- docs/api-reference.md said discovery failures answer
  `502 OPERATION_FAILED`; OPERATION_FAILED is 422 per src/types/api.ts
  and the error-code table earlier in the same file.
- The periodic re-discovery sweep (server.ts) never read
  customModelEndpointsEnabled, so turning the feature off left
  Codeman polling every saved endpoint forever. Added
  readCustomModelEndpointsEnabled() (custom-model-routes.ts, same
  shape as readPlanUsageTelemetryEnabled) and gated the interval
  callback on it.
- Reverted the formatting-only Prettier pass docs/api-reference.md
  picked up (table padding, *x* to _x_, JSON re-indent) by re-merging
  the new Custom Model Endpoints section onto the pre-PR file, so the
  diff is reviewable. No prose content was lost -- verified by diffing
  the result against the pre-revert file (formatting-only) and against
  the merge-base file (only the new section added).
- docs/custom-model-endpoints.md now states that a custom-model Claude
  session's isolated CLAUDE_CONFIG_DIR loses the user's global
  settings.json, user-level skills/agents/commands, and MCP servers
  from ~/.claude.json -- only `projects` is symlinked back.

Design question left open in the review (does `confirmed: true` need
to be two flags so "launch anyway" on the context warning doesn't also
skip the llama-swap displacement warning): keeping the single flag, as
offered. The 20s displacement sweep still catches a resulting swap
after the fact, so it's a surprise rather than a silent failure, and
splitting it is real behavioural surface I have no way to verify live
in this environment.

`npm run test:browser` could not be run in this environment (no tmux,
no downloaded Playwright browser binary) -- none of its suite's files
touch code this fix changes, but it still needs a real pass before
merge, same as any frontend change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ea59JhUmHBm1gRCsiYF33R

src/web/public/styles.css

@@ -8526,8 +8526,8 @@ kbd {
 
 .toast-message {
   flex: 1;
-  /* Errors are sticky by default (showToast) precisely so a longer, specific
-     message survives to be read — let it wrap instead of clipping. */
+  /* A sticky toast (showToast's opts.duration: 0) can carry a longer, specific
+     message — let it wrap instead of clipping. */
   white-space: pre-wrap;
   word-break: break-word;
 }
@@ -8588,6 +8588,15 @@ kbd {
   transform: translate(-50%, -50%) scale(1);
 }
 
+/* `hidden` has to be re-asserted over the `display: flex` above, or `dismiss()`
+   setting `el.hidden = true` does nothing (same trap as `.home-sessions[hidden]`
+   below): the card stays laid out at `opacity: 0` with its text/cancel/close
+   children still `pointer-events: auto`, an invisible click-blocker dead centre
+   over the terminal until the page reloads. */
+.center-status-banner[hidden] {
+  display: none;
+}
+
 .center-status-spinner {
   flex-shrink: 0;
   width: 18px;

src/web/routes/custom-model-routes.ts

@@ -16,7 +16,7 @@
 
 import type { FastifyInstance, FastifyRequest } from 'fastify';
 import { ApiErrorCode, createErrorResponse, type ApiResponse } from '../../types.js';
-import { isAdmin, parseBody } from '../route-helpers.js';
+import { isAdmin, parseBody, readJsonConfig, SETTINGS_PATH } from '../route-helpers.js';
 import { isMultiUserMode } from '../../config/multiuser.js';
 import { getDataDir } from '../../config/instance.js';
 import { isBlockedWebviewUrl } from '../webview-egress-policy.js';
@@ -565,6 +565,19 @@ function applyDiscoveredModels(host: CustomModelHost, result: DiscoveryResult):
   };
 }
 
+/**
+ * `customModelEndpointsEnabled` defaults OFF (unlike `showPlanUsageLimits`'s
+ * absent-means-on in `readPlanUsageTelemetryEnabled`), so mirror the frontend's
+ * own gate (`session-ui.js`'s `!settings.customModelEndpointsEnabled`) rather
+ * than that reader's default. Exists so the periodic re-discovery sweep in
+ * server.ts can skip entirely while the feature is off, instead of polling
+ * every saved endpoint forever regardless of the setting.
+ */
+export async function readCustomModelEndpointsEnabled(): Promise<boolean> {
+  const settings = await readJsonConfig<Record<string, unknown>>(SETTINGS_PATH, 'settings.json', {});
+  return settings.customModelEndpointsEnabled === true;
+}
+
 /**
  * Re-discovers every saved endpoint's models, best-effort. One endpoint being
  * unreachable (powered off, wrong network) must not stop the others from

src/web/routes/index.ts

@@ -30,6 +30,7 @@ export { registerTabLayoutRoutes } from './tab-layout-routes.js';
 export {
   registerCustomModelRoutes,
   refreshAllCustomModelHosts,
+  readCustomModelEndpointsEnabled,
   detectCustomModelSwapDisplacements,
   pruneIdleLlamaSwapLogTails,
   type CustomModelSessionLike,

src/web/server.ts

@@ -191,6 +191,7 @@ import {
   registerTabLayoutRoutes,
   registerCustomModelRoutes,
   refreshAllCustomModelHosts,
+  readCustomModelEndpointsEnabled,
   detectCustomModelSwapDisplacements,
   pruneIdleLlamaSwapLogTails,
   tryWebviewRefererFallback,
@@ -2761,9 +2762,18 @@ export class WebServer extends EventEmitter {
     if (!this.testMode) {
       this.cleanup.setInterval(
         () => {
-          refreshAllCustomModelHosts().catch((err) => {
-            console.error('[custom-model] periodic re-discovery failed:', getErrorMessage(err));
-          });
+          // Reads the setting fresh on every tick, same reasoning as
+          // readPlanUsageTelemetryEnabled() beside it: a live toggle takes effect
+          // on the very next cycle, not just at server boot, and turning the
+          // feature off actually stops the polling instead of only hiding the UI.
+          void readCustomModelEndpointsEnabled()
+            .then((enabled) => {
+              if (!enabled) return;
+              return refreshAllCustomModelHosts();
+            })
+            .catch((err) => {
+              console.error('[custom-model] periodic re-discovery failed:', getErrorMessage(err));
+            });
         },
         CUSTOM_MODEL_REDISCOVER_INTERVAL_MS,
         { description: 'custom model endpoint re-discovery' }