feat: add task directory mapping store

- Create taskDirectoryStore with localStorage persistence
- Support two-level mapping (taskId → dir, repoKey → dir)
- Auto-map tasks to existing repo clones
- Use existing expandTildePath utility

Foundation for PR #3 (directory integration).

Author: lucasheriques

src/renderer/stores/taskDirectoryStore.ts

@@ -0,0 +1,95 @@
+import { expandTildePath } from "@utils/path";
+import { create } from "zustand";
+import { persist } from "zustand/middleware";
+
+interface TaskDirectoryState {
+  // Direct task-to-directory mappings
+  taskDirectories: Record<string, string>;
+
+  // Repository-to-directory mappings (enables repo reuse across tasks)
+  repoDirectories: Record<string, string>;
+
+  // Get directory for a task (checks task mapping first, then repo mapping)
+  getTaskDirectory: (taskId: string, repoKey?: string) => string | null;
+
+  // Set directory for a specific task
+  setTaskDirectory: (taskId: string, directory: string) => void;
+
+  // Set directory for a repository (shared across tasks)
+  setRepoDirectory: (repoKey: string, directory: string) => void;
+
+  // Remove task directory mapping
+  clearTaskDirectory: (taskId: string) => void;
+
+  // Remove repository directory mapping
+  clearRepoDirectory: (repoKey: string) => void;
+}
+
+export const useTaskDirectoryStore = create<TaskDirectoryState>()(
+  persist(
+    (set, get) => ({
+      taskDirectories: {},
+      repoDirectories: {},
+
+      getTaskDirectory: (taskId: string, repoKey?: string) => {
+        // 1. Check for direct task mapping
+        const taskDir = get().taskDirectories[taskId];
+        if (taskDir) {
+          return expandTildePath(taskDir);
+        }
+
+        // 2. Check for repo mapping (if repoKey provided)
+        if (repoKey) {
+          const repoDir = get().repoDirectories[repoKey];
+          if (repoDir) {
+            // Auto-map task to this directory for convenience
+            get().setTaskDirectory(taskId, repoDir);
+            return expandTildePath(repoDir);
+          }
+        }
+
+        // 3. No mapping found
+        return null;
+      },
+
+      setTaskDirectory: (taskId: string, directory: string) => {
+        set((state) => ({
+          taskDirectories: {
+            ...state.taskDirectories,
+            [taskId]: directory,
+          },
+        }));
+      },
+
+      setRepoDirectory: (repoKey: string, directory: string) => {
+        set((state) => ({
+          repoDirectories: {
+            ...state.repoDirectories,
+            [repoKey]: directory,
+          },
+        }));
+      },
+
+      clearTaskDirectory: (taskId: string) => {
+        set((state) => {
+          const { [taskId]: _, ...rest } = state.taskDirectories;
+          return { taskDirectories: rest };
+        });
+      },
+
+      clearRepoDirectory: (repoKey: string) => {
+        set((state) => {
+          const { [repoKey]: _, ...rest } = state.repoDirectories;
+          return { repoDirectories: rest };
+        });
+      },
+    }),
+    {
+      name: "task-directory-mappings",
+      partialize: (state) => ({
+        taskDirectories: state.taskDirectories,
+        repoDirectories: state.repoDirectories,
+      }),
+    },
+  ),
+);