fix: improve error handling across Rust and TypeScript

- Log swallowed errors in file watcher and window operations (lib.rs, watcher.rs)
- Propagate recovery errors from bridge::recover_pending to SyncResult.errors
  so the frontend can display them instead of silently dropping failures
- Fix useTauriEvent/useTauriEvents race condition where cleanup fires before
  async listen() resolves, leaking the listener (cancelled flag pattern)
- Guard computeStaleness against invalid date strings (NaN -> 'normal'
  instead of incorrectly returning 'urgent')
- Strengthen isMcError type guard to check field types, not just presence
- Log warning when data directory resolution falls back to '.' (state.rs, bridge.rs)
- Add test for computeStaleness with invalid date inputs

tests/lib/types.test.ts

@@ -31,6 +31,12 @@ describe("computeStaleness", () => {
     ).toISOString();
     expect(computeStaleness(tenDaysAgo)).toBe("urgent");
   });
+
+  it("returns 'normal' for invalid date strings instead of 'urgent'", () => {
+    expect(computeStaleness("not-a-date")).toBe("normal");
+    expect(computeStaleness("")).toBe("normal");
+    expect(computeStaleness("2026-13-99T99:99:99Z")).toBe("normal");
+  });
 });
 
 describe("isMcError", () => {