refactor: Remove cross-store dependencies using Zustand event store

Replace direct store imports and calls with a Zustand-based event system
for decoupled cross-store communication.

Changes:
- Created storeEvents.ts using Zustand for event management
- Removed direct usePatternStore import from useMachineStore
- Removed dynamic imports for useMachineUploadStore and useMachineCacheStore
- Added event subscriptions in usePatternStore, useMachineUploadStore, and useMachineCacheStore
- useMachineStore now emits patternDeleted event instead of calling other stores directly

Benefits:
- Stores can be tested in isolation
- No tight coupling between stores
- Clear, explicit event-driven data flow
- Uses Zustand's built-in subscription system
- Easier to refactor stores independently

Fixes #37

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/stores/storeEvents.ts

@@ -0,0 +1,44 @@
+/**
+ * Store Events
+ *
+ * Zustand-based event store for cross-store communication without tight coupling.
+ * Uses Zustand's built-in subscription system to emit and react to events.
+ */
+
+import { create } from "zustand";
+
+interface EventState {
+  // Event counters - incrementing these triggers subscriptions
+  patternDeletedCount: number;
+
+  // Actions to emit events
+  emitPatternDeleted: () => void;
+}
+
+/**
+ * Event store using Zustand for cross-store communication.
+ * Stores can emit events by calling actions, and subscribe to events using Zustand's subscribe.
+ */
+export const useEventStore = create<EventState>((set) => ({
+  patternDeletedCount: 0,
+
+  emitPatternDeleted: () => {
+    set((state) => ({ patternDeletedCount: state.patternDeletedCount + 1 }));
+  },
+}));
+
+/**
+ * Subscribe to pattern deleted event
+ * @param callback - Function to call when event is emitted
+ * @returns Unsubscribe function
+ */
+export const onPatternDeleted = (callback: () => void): (() => void) => {
+  let prevCount = useEventStore.getState().patternDeletedCount;
+
+  return useEventStore.subscribe((state) => {
+    if (state.patternDeletedCount !== prevCount) {
+      prevCount = state.patternDeletedCount;
+      callback();
+    }
+  });
+};

src/stores/useMachineCacheStore.ts

@@ -1,6 +1,7 @@
 import { create } from "zustand";
 import type { PesPatternData } from "../formats/import/pesImporter";
 import { uuidToString } from "../services/PatternCacheService";
+import { onPatternDeleted } from "./storeEvents";
 
 /**
  * Machine Cache Store
@@ -192,3 +193,8 @@ export const useMachineCacheStore = create<MachineCacheState>((set, get) => ({
     });
   },
 }));
+
+// Subscribe to pattern deleted event
+onPatternDeleted(() => {
+  useMachineCacheStore.getState().clearResumeState();
+});

src/stores/useMachineStore.ts

@@ -13,7 +13,7 @@ import { SewingMachineError } from "../utils/errorCodeHelpers";
 import { uuidToString } from "../services/PatternCacheService";
 import { createStorageService } from "../platform";
 import type { IStorageService } from "../platform/interfaces/IStorageService";
-import { usePatternStore } from "./usePatternStore";
+import { useEventStore } from "./storeEvents";
 
 interface MachineState {
   // Service instances
@@ -291,16 +291,8 @@ export const useMachineStore = create<MachineState>((set, get) => ({
         sewingProgress: null,
       });
 
-      // Clear uploaded pattern data in pattern store
-      usePatternStore.getState().clearUploadedPattern();
-
-      // Clear upload state in upload store
-      const { useMachineUploadStore } = await import("./useMachineUploadStore");
-      useMachineUploadStore.getState().reset();
-
-      // Clear resume state in cache store
-      const { useMachineCacheStore } = await import("./useMachineCacheStore");
-      useMachineCacheStore.getState().clearResumeState();
+      // Emit pattern deleted event for other stores to react
+      useEventStore.getState().emitPatternDeleted();
 
       await refreshStatus();
     } catch (err) {

src/stores/useMachineUploadStore.ts

@@ -1,6 +1,7 @@
 import { create } from "zustand";
 import type { PesPatternData } from "../formats/import/pesImporter";
 import { uuidToString } from "../services/PatternCacheService";
+import { onPatternDeleted } from "./storeEvents";
 
 /**
  * Machine Upload Store
@@ -126,3 +127,8 @@ export const useMachineUploadStore = create<MachineUploadState>((set) => ({
     set({ uploadProgress: 0, isUploading: false });
   },
 }));
+
+// Subscribe to pattern deleted event
+onPatternDeleted(() => {
+  useMachineUploadStore.getState().reset();
+});

src/stores/usePatternStore.ts

@@ -1,5 +1,6 @@
 import { create } from "zustand";
 import type { PesPatternData } from "../formats/import/pesImporter";
+import { onPatternDeleted } from "./storeEvents";
 
 interface PatternState {
   // Original pattern (pre-upload)
@@ -121,3 +122,8 @@ export const useUploadedPatternOffset = () =>
   usePatternStore((state) => state.uploadedPatternOffset);
 export const usePatternRotation = () =>
   usePatternStore((state) => state.patternRotation);
+
+// Subscribe to pattern deleted event
+onPatternDeleted(() => {
+  usePatternStore.getState().clearUploadedPattern();
+});