fix(web): prevent 404 on workspace switch and downgrade 404 log level

- Skip issue refetch when store is cleared during workspace switch by
  tracking which issue was already loaded (loadedIdRef pattern)
- Downgrade 404 responses from logger.error to logger.warn in ApiClient
  since resource-not-found is a normal business response, not a bug

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/features/issues/components/issue-detail.tsx

@@ -196,12 +196,22 @@ export function IssueDetail({ issueId, onDelete, defaultSidebarOpen = true, layo
   const issue = useIssueStore((s) => s.issues.find((i) => i.id === id)) ?? null;
   const [issueLoading, setIssueLoading] = useState(!issue);
 
-  // If issue isn't in the store yet, fetch and upsert it
+  // If issue isn't in the store yet, fetch and upsert it.
+  // loadedIdRef tracks which issue was already loaded — if it disappears
+  // from the store (workspace switch clears all issues), skip refetch.
+  const loadedIdRef = useRef<string | null>(null);
   useEffect(() => {
     if (issue) {
+      loadedIdRef.current = id;
       setIssueLoading(false);
       return;
     }
+    // Issue was loaded for this id but vanished → store cleared (workspace switch)
+    if (loadedIdRef.current === id) {
+      loadedIdRef.current = null;
+      return;
+    }
+    // Issue not in store → fetch it
     setIssueLoading(true);
     api
       .getIssue(id)

apps/web/shared/api/client.ts

@@ -113,7 +113,8 @@ export class ApiClient {
     if (!res.ok) {
       if (res.status === 401) this.handleUnauthorized();
       const message = await this.parseErrorMessage(res, `API error: ${res.status} ${res.statusText}`);
-      this.logger.error(`← ${res.status} ${path}`, { rid, duration: `${Date.now() - start}ms`, error: message });
+      const logLevel = res.status === 404 ? "warn" : "error";
+      this.logger[logLevel](`← ${res.status} ${path}`, { rid, duration: `${Date.now() - start}ms`, error: message });
       throw new Error(message);
     }