feat(04-03): initialize FileWatcher in main.rs and wire App constructor

- Create FileWatcher watching index.md's parent directory before App::new()
- Pass file_watcher Option to App::new() as seventh argument
- Watcher failure is non-fatal: prints warning and passes None to App

src/main.rs

@@ -77,6 +77,24 @@ fn main() {
             }
         };
 
+    // 3c. Initialize filesystem watcher for live content refresh.
+    //     Watch the parent directory of index.md (or vault root if index.md is at root).
+    //     Watcher must be created before App::new() so it can be passed in.
+    let file_watcher = {
+        let watch_dir = app_config.vault_path.join("index.md")
+            .parent()
+            .map(|p| p.to_path_buf())
+            .unwrap_or_else(|| app_config.vault_path.clone());
+        match app::FileWatcher::new(&watch_dir) {
+            Ok(w) => Some(w),
+            Err(e) => {
+                // Non-fatal: live reload won't work but app is still usable
+                eprintln!("Warning: filesystem watcher unavailable: {}", e);
+                None
+            }
+        }
+    };
+
     // ── TERMINAL PHASE ────────────────────────────────────────────────────────
     // Install safety envelope BEFORE terminal init so panics during init are caught.
 
@@ -115,6 +133,7 @@ fn main() {
         raw_content,
         initial_link_records,
         "index.md".to_string(),
+        file_watcher,
     );
     let shutdown_reason = app_state.run_event_loop(&mut term, &signal_flags);