feat: implemented select all notes feature.

src/util/selectionUtil.ts

@@ -0,0 +1,56 @@
+import { KGCore } from '../core/KGCore';
+import { useProjectStore } from '../stores/projectStore';
+import { KGMidiRegion } from '../core/region/KGMidiRegion';
+import { KGTrack } from '../core/track/KGTrack';
+import { KGMidiNote } from '../core/midi/KGMidiNote';
+
+/**
+ * Select all notes in the active region if the piano roll is visible.
+ * Logs the count and region id on success.
+ * Returns true if selection was performed; false otherwise.
+ */
+export const selectAllNotesInActiveRegion = (): boolean => {
+  const { showPianoRoll, activeRegionId, updateTrack } = useProjectStore.getState();
+  if (!showPianoRoll || !activeRegionId) {
+    return false;
+  }
+
+  try {
+    const core = KGCore.instance();
+    const project = core.getCurrentProject();
+    const tracks = project.getTracks();
+
+    let parentTrack: KGTrack | null = null;
+    let activeRegion: KGMidiRegion | null = null;
+
+    for (const track of tracks) {
+      const region = track.getRegions().find(r => r.getId() === activeRegionId);
+      if (region && region instanceof KGMidiRegion) {
+        parentTrack = track as KGTrack;
+        activeRegion = region as KGMidiRegion;
+        break;
+      }
+    }
+
+    if (!activeRegion || !parentTrack) {
+      return false;
+    }
+
+    // Clear previous selection and select all notes in the region
+    core.clearSelectedItems();
+    const notes: KGMidiNote[] = activeRegion.getNotes();
+    notes.forEach((n: KGMidiNote) => n.select());
+    core.addSelectedItems(notes);
+
+    // Update track to persist selection state in model/UI
+    updateTrack(parentTrack);
+
+    console.log(`Selected all notes: count=${notes.length}, regionId=${activeRegionId}`);
+    return true;
+  } catch (error) {
+    console.error('Select all notes failed:', error);
+    return false;
+  }
+};
+
+