fix: optimize serve/sourcemap startup from >180s to ~8s

Root cause: notify-debouncer-full with macos_kqueue caused 25K+
directory watch registrations to take >170s on large projects.

Changes:
- Replace notify-debouncer-full with notify-debouncer-mini to avoid
  FSEvents Create+Remove event cancellation and heavy per-watch overhead
- Remove macos_kqueue feature; use FSEvents (matches upstream Rojo)
- Fix VFS read guard: watch_enabled && watch_recursive -> watch_enabled
  so recording mechanism works when watch_recursive is false
- Build RefPathIndex from patch_apply data instead of redundant 4.8s
  WalkDir + 5,854 file re-reads (populate_from_dir)
- Use ServeSession::new_oneshot() for sourcemap without --watch
- Restore simple synchronous watch setup (implicit during reads)

Serve: >180s (never completed) -> ~8s to Listening
Sourcemap: 14.3s -> ~9s
All 489 tests passing.

src/rojo_ref.rs

@@ -326,6 +326,22 @@ impl RefPathIndex {
         }
     }
 
+    /// Build from pre-collected entries (avoids re-walking the directory tree).
+    pub fn from_entries(entries: Vec<(String, PathBuf)>) -> Self {
+        let mut index = Self::new();
+        let count = entries.len();
+        for (ref_path, meta_file) in entries {
+            index.add(&ref_path, &meta_file);
+        }
+        if count > 0 {
+            log::debug!(
+                "RefPathIndex: built from {} collected Rojo_Ref_* entries",
+                count
+            );
+        }
+        index
+    }
+
     /// Record that `meta_file` contains a `Rojo_Ref_*` attribute with value
     /// `ref_path` (the instance path string, e.g., "Workspace/Model/Part1").
     pub fn add(&mut self, ref_path: &str, meta_file: &Path) {