feat: add Tauri state persistence and BvCli trait

- Add Tauri storage adapter for Zustand (tauri-storage.ts)
- Add read_state, write_state, clear_state Tauri commands
- Wire focus-store and nav-store to use Tauri persistence
- Add BvCli trait for bv CLI mocking with response types
- Add BvError and McError conversion for bv errors
- Add cleanup_tmp_files tests for bridge
- Fix linter-introduced tauri_specta::command issues

Closes bd-2x6, bd-gil, bd-3px

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

src/lib/tauri-storage.ts

@@ -0,0 +1,109 @@
+/**
+ * Tauri storage adapter for Zustand persist middleware.
+ *
+ * Stores Zustand state in `~/.local/share/mc/state.json` via Tauri backend
+ * instead of browser localStorage. Falls back to localStorage in browser context.
+ */
+
+import { invoke } from "@tauri-apps/api/core";
+import type { StateStorage } from "zustand/middleware";
+
+/**
+ * Create a storage adapter that persists to Tauri backend.
+ *
+ * Uses the `read_state`, `write_state`, and `clear_state` Tauri commands.
+ */
+export function createTauriStorage(): StateStorage {
+  return {
+    getItem: async (_name: string): Promise<string | null> => {
+      try {
+        const state = await invoke<Record<string, unknown> | null>("read_state");
+        if (state === null) {
+          return null;
+        }
+        return JSON.stringify(state);
+      } catch (error) {
+        console.warn("[tauri-storage] Failed to read state:", error);
+        return null;
+      }
+    },
+
+    setItem: async (_name: string, value: string): Promise<void> => {
+      try {
+        const state = JSON.parse(value) as Record<string, unknown>;
+        await invoke("write_state", { state });
+      } catch (error) {
+        console.warn("[tauri-storage] Failed to write state:", error);
+      }
+    },
+
+    removeItem: async (_name: string): Promise<void> => {
+      try {
+        await invoke("clear_state");
+      } catch (error) {
+        console.warn("[tauri-storage] Failed to clear state:", error);
+      }
+    },
+  };
+}
+
+/**
+ * Check if running in Tauri context.
+ */
+function isTauriContext(): boolean {
+  return typeof window !== "undefined" && "__TAURI__" in window;
+}
+
+/**
+ * Create a localStorage-based storage adapter for browser context.
+ */
+function createLocalStorageAdapter(): StateStorage {
+  return {
+    getItem: (name: string): string | null => {
+      if (typeof window === "undefined") return null;
+      return localStorage.getItem(name);
+    },
+
+    setItem: (name: string, value: string): void => {
+      if (typeof window === "undefined") return;
+      localStorage.setItem(name, value);
+    },
+
+    removeItem: (name: string): void => {
+      if (typeof window === "undefined") return;
+      localStorage.removeItem(name);
+    },
+  };
+}
+
+/**
+ * Get the appropriate storage adapter for the current context.
+ *
+ * - In Tauri: Uses backend persistence to ~/.local/share/mc/state.json
+ * - In browser: Falls back to localStorage
+ */
+export async function initializeStorage(): Promise<StateStorage> {
+  if (isTauriContext()) {
+    return createTauriStorage();
+  }
+  return createLocalStorageAdapter();
+}
+
+/**
+ * Singleton storage instance.
+ * Use this in store definitions to avoid recreating the adapter.
+ */
+let _storage: StateStorage | null = null;
+
+/**
+ * Get the storage adapter (lazy initialization).
+ *
+ * In Tauri context, returns Tauri storage.
+ * In browser context, returns localStorage wrapper.
+ */
+export function getStorage(): StateStorage {
+  if (_storage === null) {
+    _storage = isTauriContext() ? createTauriStorage() : createLocalStorageAdapter();
+  }
+  return _storage;
+}

src/stores/focus-store.ts

@@ -6,7 +6,8 @@
  */
 
 import { create } from "zustand";
-import { persist } from "zustand/middleware";
+import { persist, createJSONStorage } from "zustand/middleware";
+import { getStorage } from "@/lib/tauri-storage";
 import type { FocusAction, FocusItem } from "@/lib/types";
 
 export interface FocusState {
@@ -108,6 +109,7 @@ export const useFocusStore = create<FocusState>()(
     }),
     {
       name: "mc-focus-store",
+      storage: createJSONStorage(() => getStorage()),
       partialize: (state) => ({
         current: state.current,
         queue: state.queue,

src/stores/nav-store.ts

@@ -6,7 +6,8 @@
  */
 
 import { create } from "zustand";
-import { persist } from "zustand/middleware";
+import { persist, createJSONStorage } from "zustand/middleware";
+import { getStorage } from "@/lib/tauri-storage";
 
 export type ViewId = "focus" | "queue" | "inbox";
 
@@ -23,6 +24,7 @@ export const useNavStore = create<NavState>()(
     }),
     {
       name: "mc-nav-store",
+      storage: createJSONStorage(() => getStorage()),
     }
   )
 );