fix(hostConfig): clear JsonRecordEditor error on unmount

When the owner prop changes (e.g. to "connection-only") the host-context
JsonRecordEditor unmounts but its error state in the parent
(hostCtxError) was never cleared. The aggregated hasError signal
stayed true and onValidityChange kept Save disabled with no visible
error in the UI for the user to fix.

Add a cleanup effect inside JsonRecordEditor that calls
onErrorChange(null) on unmount. Generalizes to any section that
becomes hidden — the parent's per-section error state mirrors only
sections that are currently rendered.

https://claude.ai/code/session_01FjxdHVhJba5KpLjXiiuuCu

Author: claude

mcpjam-inspector/client/src/components/host-config/HostConfigEditor.tsx

@@ -469,6 +469,19 @@ function JsonRecordEditor({
     lastValueRef.current = value;
   }, [value, stringified, error, setError]);
 
+  // Clear the error signal when this editor unmounts (e.g. owner
+  // switched to a mode that hides this section). Without this, the
+  // parent's aggregated hasError signal would stay stuck on a stale
+  // error from a section the user can no longer see, keeping Save
+  // disabled with no visible cause to fix.
+  useEffect(() => {
+    return () => {
+      onErrorChange?.(null);
+    };
+    // We intentionally don't depend on onErrorChange — only fire on unmount.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
   // Parse on every keystroke so errors clear as soon as the user fixes
   // them and the parent's `onChange`/`onErrorChange` signals stay live.
   // We still only call `onChange` (committing the parsed value) on