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

docs/custom-model-endpoints.md

@@ -290,7 +290,13 @@ size`. No entry for the model in `modelContextLengths` means the var is
   [`docs/wiki/Agent-CLIs.md`](wiki/Agent-CLIs.md), just applied
   automatically here. Best-effort: a platform that refuses the symlink keeps
   the pre-existing blind-response-viewer side effect rather than failing the
-  whole custom-model apply over it.
+  whole custom-model apply over it. ⚠️ **This relocates the whole `.claude`
+  tree, not just transcripts**: a custom-model Claude session also loses the
+  user's global `settings.json`, user-level skills (the codeman agent skill
+  included), user-level agents and commands, and the MCP servers configured
+  in `~/.claude.json` — none of those are symlinked back, only `projects` is.
+  A fine trade for "point this session at my local llama.cpp," but worth
+  knowing before it surprises you mid-session.
 
 **That isolated directory needed one more fix to actually be usable
 non-interactively.** An otherwise-empty `CLAUDE_CONFIG_DIR` has none of a