fix(review): close 5 follow-up gaps from Stage 6 audit re-review

- F-T-003 actually closed: clients/typescript/src/subscribe.ts now
  bounds the 401-refresh loop at 3 consecutive refusals, surfaces an
  onError describing the loop, and resets on any successful stream
  open. New test covers the cap. The Stage 2 dashboard fix only
  addressed adminRequest in dashboard/src/lib/api.ts; the originally-
  cited TS client file was untouched.

- users/invitations subtab dropped the redundant api.apps.get fetch
  the other 5 subtabs already shed in Stage 6.

- Queue visibility-timeout validator pulled out as
  validate_queue_visibility_timeout, with two thresholds: hard-reject
  below MIN_QUEUE_VISIBILITY_TIMEOUT_SECS (30s — catches typos), warn-
  log between MIN and SAFE_VISIBILITY_VS_EXEC_BUDGET_SECS (300s) so
  operators see when their visibility is below the dispatcher's
  per-message executor budget. Stage 6 only had the hard floor; the
  reviewer caught that a 60s handler still races a 30s visibility
  even after the floor. Four new unit tests cover none/above-safe/
  between/below-min.

- pic dead-letters count subcommand: cheap headless probe for
  unresolved DL totals, parallels the dashboard's badge query.

- pic dead-letters replay now has a happy-path integration test
  (replay_against_real_dl_row_succeeds): inserts a synthetic DL row
  directly via the rust-postgres sync driver (added as dev-dep),
  drives `pic dead-letters replay`, asserts the row is resolved with
  reason=replayed and count drops back to 0. Plus a count smoke test.

All 75 CLI integration tests + 16 TS client tests + 4 new
visibility-timeout unit tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/routes/apps/[slug]/users/invitations/+page.svelte

@@ -1,11 +1,10 @@
 <script lang="ts">
 	import { base } from '$app/paths';
 	import { page } from '$app/state';
-	import { api, ApiError, type App, type Invitation } from '$lib/api';
+	import { api, ApiError, type Invitation } from '$lib/api';
 	import ConfirmModal from '$lib/ConfirmModal.svelte';
 
 	let slug = $derived(page.params.slug ?? '');
-	let app = $state<App | null>(null);
 	let invitations = $state<Invitation[]>([]);
 	let loading = $state(false);
 	let error = $state<string | null>(null);
@@ -26,14 +25,6 @@
 	let toRevoke = $state<Invitation | null>(null);
 	let revoking = $state(false);
 
-	async function loadApp() {
-		try {
-			app = await api.apps.get(slug);
-		} catch (e) {
-			error = e instanceof ApiError ? e.message : String(e);
-		}
-	}
-
 	async function loadInvitations() {
 		loading = true;
 		error = null;
@@ -49,7 +40,6 @@
 
 	$effect(() => {
 		void slug;
-		void loadApp();
 		void loadInvitations();
 	});