fix(files): keep text opens working after content-cache dispose

React Strict Mode disposed the memoized content-cache owner while the
provider kept reusing it, so validateContextFileOpen threw before any
/api/fs/read and toasted "Failed to open file" for notes.txt. Binaries
still opened because they skip the pre-read. Serve uncached reads from
disposed owners, clear cache on runtime switch without deactivating, and
own the cache lifecycle in an effect.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/contexts/RuntimeAPIProvider.tsx

@@ -1,17 +1,32 @@
 import React, { type JSX, type ReactNode } from 'react';
 import { RuntimeAPIContext } from '@/contexts/runtimeAPIContext';
-import type { RuntimeAPIs } from '@/lib/api/types';
+import type { FilesAPI, RuntimeAPIs } from '@/lib/api/types';
 import { createContentCachedFiles } from '@/contexts/content-cache-owner';
 
+type ContentCachedFiles = ReturnType<typeof createContentCachedFiles>;
+
 export function RuntimeAPIProvider({ apis, children }: { apis: RuntimeAPIs; children: ReactNode }): JSX.Element {
-  const cachedFiles = React.useMemo(() => createContentCachedFiles(apis.files), [apis.files]);
-  React.useEffect(() => () => cachedFiles.dispose(), [cachedFiles]);
+  // Effect-owned lifecycle: React Strict Mode dispose+remount must create a fresh
+  // owner. useMemo + dispose reused a dead owner and broke text-file opens
+  // (binaries skipped the pre-read, so they still appeared to work).
+  const [cachedOwner, setCachedOwner] = React.useState<ContentCachedFiles | null>(null);
+
+  React.useEffect(() => {
+    const owner = createContentCachedFiles(apis.files);
+    setCachedOwner(owner);
+    return () => {
+      owner.dispose();
+      setCachedOwner((current) => (current === owner ? null : current));
+    };
+  }, [apis.files]);
+
+  const files: FilesAPI = cachedOwner?.files ?? apis.files;
   const cachedApis = React.useMemo<RuntimeAPIs>(
     () => ({
       ...apis,
-      files: cachedFiles.files,
+      files,
     }),
-    [apis, cachedFiles],
+    [apis, files],
   );
   return <RuntimeAPIContext.Provider value={cachedApis}>{children}</RuntimeAPIContext.Provider>;
 }