review: harden version read + fix MonitoringScreen docstring

Address PR #1641 review feedback:

- Add readInspectorVersionSafe() (non-throwing) in core/node/version.ts and use
  it in the web backend, so a failure to resolve the root manifest hides the
  (cosmetic) version badge instead of crashing the backend at startup. Covered
  by tests for both the resolved and unresolvable paths.
- Update MonitoringScreen's docstrings: it now wraps every supplied screen in a
  ScreenStage (only the active tab mounts, cross-fading) rather than rendering
  just the active tab's node.

The third fetch-consolidation suggestion (one useInitialConfig instead of three
GET /api/config hooks) is tracked as a follow-up in #1643.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BrihGWcrM9JGRyu41nzZYw

core/node/version.ts

@@ -64,3 +64,23 @@ export function readInspectorVersion(callerUrl: string): string {
     `Could not locate the ${ROOT_PACKAGE_NAME} root package.json above ${startDir}`,
   );
 }
+
+/**
+ * Non-throwing variant of {@link readInspectorVersion}: returns `undefined`
+ * instead of throwing when the root manifest can't be resolved. For callers
+ * where the version is cosmetic (e.g. the web backend surfacing it to the
+ * browser) — a resolution failure should hide the version, not take the caller
+ * down at startup.
+ *
+ * @param callerUrl the calling module's `import.meta.url`
+ * @returns the root version, or `undefined` if it can't be resolved
+ */
+export function readInspectorVersionSafe(
+  callerUrl: string,
+): string | undefined {
+  try {
+    return readInspectorVersion(callerUrl);
+  } catch {
+    return undefined;
+  }
+}