fix: hide empty-state copy on queue credential fail-closed (Closes #458)

When fetch_error is set, render only the unavailable banner and an
explicit not-fetched inventory note. Suppress queue tables, pagination
proof, and "No open items." copy that implied a successful empty fetch.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

webui/queue_views.py

@@ -72,6 +72,18 @@ def render_queue_page(snapshot: QueueSnapshot) -> str:
             f'<div class="stub"><p><strong>Queue unavailable:</strong> '
             f"{html.escape(snapshot.fetch_error)}</p></div>"
         )
+        inventory_block = (
+            "<p class='muted'><strong>Inventory:</strong> not fetched "
+            "(fail closed — queue tables omitted).</p>"
+        )
+        return (
+            "<h2>Live queue</h2>"
+            f"<p class='meta'>Repository: <code>{html.escape(snapshot.repo_label)}</code> "
+            f"· project <code>{html.escape(snapshot.project_id)}</code></p>"
+            f"{error_block}"
+            f"{inventory_block}"
+            "<p class='muted'>Read-only MVP — claims, reviews, and merges stay in Gitea/MCP tools.</p>"
+        )
 
     pr_section = _queue_table(
         title="Open pull requests",
@@ -101,7 +113,6 @@ def render_queue_page(snapshot: QueueSnapshot) -> str:
         "<h2>Live queue</h2>"
         f"<p class='meta'>Repository: <code>{html.escape(snapshot.repo_label)}</code> "
         f"· project <code>{html.escape(snapshot.project_id)}</code></p>"
-        f"{error_block}"
         f"{_pagination_html('PR', snapshot.pr_pagination)}"
         f"{pr_section}"
         f"{_pagination_html('Issue', snapshot.issue_pagination)}"