feat(engine): costs on start, unlock checks, queue completion advancement

src/engine/__tests__/save.test.ts

@@ -86,7 +86,8 @@ describe('applyOfflineProgress()', () => {
     startAction(state, content, 'forage'); // 3000ms per gold
     const credited = applyOfflineProgress(state, content, 1000, 1000 + 9000); // 9s
     expect(credited).toBe(9000);
-    expect(state.resources.gold).toBe(3); // 9000 / 3000
+    expect(state.resources.gold).toBe(1); // one completion then idle
+    expect(state.activeActionId).toBeNull();
   });
 
   it('credits nothing when the clock did not advance', () => {
@@ -103,6 +104,7 @@ describe('applyOfflineProgress()', () => {
     startAction(state, content, 'forage');
     const credited = applyOfflineProgress(state, content, 0, 10_000_000, 6000);
     expect(credited).toBe(6000);
-    expect(state.resources.gold).toBe(2); // 6000 / 3000
+    expect(state.resources.gold).toBe(1); // one completion then idle
+    expect(state.activeActionId).toBeNull();
   });
 });