feat(FN-4606): complete Step 1 — settings schema and types

Ref: Runfusion/Fusion#321
Fusion-Task-Id: FN-4606
Fusion-Task-Lineage: 94b23f37-944e-4bcd-bfa1-67d0a8c0a267

packages/core/src/__tests__/store-settings.test.ts

@@ -37,6 +37,18 @@ describe("TaskStore", () => {
     });
   });
 
+  describe("worktreesDir setting", () => {
+    it("round-trips worktreesDir via updateSettings and project serialization", async () => {
+      await harness.store().updateSettings({ worktreesDir: "~/.fn-worktrees/{repo}" });
+      const settings = await harness.store().getSettings();
+      expect(settings.worktreesDir).toBe("~/.fn-worktrees/{repo}");
+
+      const configRaw = await readFile(join(harness.rootDir(), ".fusion", "config.json"), "utf-8");
+      const config = JSON.parse(configRaw);
+      expect(config.settings.worktreesDir).toBe("~/.fn-worktrees/{repo}");
+    });
+  });
+
   describe("autoResolveConflicts setting", () => {
     it("persists autoResolveConflicts and returns it via getSettings", async () => {
       await harness.store().updateSettings({ autoResolveConflicts: false });

packages/core/src/settings-schema.ts

@@ -192,6 +192,7 @@ export const DEFAULT_PROJECT_SETTINGS = {
   recycleWorktrees: false,
   executorAllowSiblingBranchRename: false,
   worktreeNaming: "random",
+  worktreesDir: undefined,
   taskPrefix: "FN",
   includeTaskIdInCommit: true,
   commitAuthorEnabled: true,

packages/core/src/types.ts

@@ -2394,6 +2394,13 @@ export interface ProjectSettings {
    *  - "task-title": Use a slugified version of the task title (e.g., fix-login-bug)
    *  Default: "random". */
   worktreeNaming?: "random" | "task-id" | "task-title";
+  /** Optional container directory for task worktrees.
+   *  When unset, worktrees default to `<projectRoot>/.worktrees`.
+   *  Supports leading `~` expansion and the `{repo}` token (basename of the project root).
+   *  Accepts absolute paths or paths relative to the project root.
+   *  Affects newly-created worktrees and pool/self-healing directory scans only;
+   *  existing `task.worktree` absolute paths are honored as-is. */
+  worktreesDir?: string;
   /** Prefix for generated task IDs (e.g. `"KB"` produces `KB-001`).
    *  Defaults to `"KB"`. Only affects new tasks — existing tasks retain
    *  their original IDs. */