feat(FN-936): add modal description persistence for re-entry

- Add modalPersistence hook for saving/restoring modal state (description, goal) via localStorage
- Update PlanningModeModal to persist and restore description across re-opens
- Update SubtaskBreakdownModal to persist and clear description on resume flow
- Update MissionInterviewModal to clear goal after starting interview
- Add unit tests for modalPersistence hook
- Add integration tests for modal re-entry behavior across all three modals
- Add changeset for published package patch bump

packages/dashboard/app/hooks/__tests__/modalPersistence.test.ts

@@ -0,0 +1,144 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import {
+  STORED_PLANNING_KEY,
+  STORED_SUBTASK_KEY,
+  STORED_MISSION_KEY,
+  savePlanningDescription,
+  getPlanningDescription,
+  clearPlanningDescription,
+  saveSubtaskDescription,
+  getSubtaskDescription,
+  clearSubtaskDescription,
+  saveMissionGoal,
+  getMissionGoal,
+  clearMissionGoal,
+} from "../modalPersistence";
+
+describe("modalPersistence", () => {
+  beforeEach(() => {
+    localStorage.clear();
+  });
+
+  describe("Storage keys are exported", () => {
+    it("exports planning key", () => {
+      expect(STORED_PLANNING_KEY).toBe("kb-planning-last-description");
+    });
+
+    it("exports subtask key", () => {
+      expect(STORED_SUBTASK_KEY).toBe("kb-subtask-last-description");
+    });
+
+    it("exports mission key", () => {
+      expect(STORED_MISSION_KEY).toBe("kb-mission-last-goal");
+    });
+  });
+
+  describe("Planning persistence", () => {
+    it("saves and retrieves planning description", () => {
+      savePlanningDescription("Build authentication");
+      expect(getPlanningDescription()).toBe("Build authentication");
+    });
+
+    it("returns empty string when nothing saved", () => {
+      expect(getPlanningDescription()).toBe("");
+    });
+
+    it("clears correctly", () => {
+      savePlanningDescription("Test");
+      clearPlanningDescription();
+      expect(getPlanningDescription()).toBe("");
+    });
+
+    it("returns empty string when localStorage returns null", () => {
+      vi.spyOn(Storage.prototype, "getItem").mockReturnValue(null);
+      expect(getPlanningDescription()).toBe("");
+      vi.restoreAllMocks();
+    });
+
+    it("overwrites previous value", () => {
+      savePlanningDescription("First");
+      savePlanningDescription("Second");
+      expect(getPlanningDescription()).toBe("Second");
+    });
+  });
+
+  describe("Subtask persistence", () => {
+    it("saves and retrieves subtask description", () => {
+      saveSubtaskDescription("Implement login feature");
+      expect(getSubtaskDescription()).toBe("Implement login feature");
+    });
+
+    it("returns empty string when nothing saved", () => {
+      expect(getSubtaskDescription()).toBe("");
+    });
+
+    it("clears correctly", () => {
+      saveSubtaskDescription("Test");
+      clearSubtaskDescription();
+      expect(getSubtaskDescription()).toBe("");
+    });
+
+    it("overwrites previous value", () => {
+      saveSubtaskDescription("First");
+      saveSubtaskDescription("Second");
+      expect(getSubtaskDescription()).toBe("Second");
+    });
+  });
+
+  describe("Mission persistence", () => {
+    it("saves and retrieves mission goal", () => {
+      saveMissionGoal("Build a SaaS platform");
+      expect(getMissionGoal()).toBe("Build a SaaS platform");
+    });
+
+    it("returns empty string when nothing saved", () => {
+      expect(getMissionGoal()).toBe("");
+    });
+
+    it("clears correctly", () => {
+      saveMissionGoal("Test");
+      clearMissionGoal();
+      expect(getMissionGoal()).toBe("");
+    });
+
+    it("overwrites previous value", () => {
+      saveMissionGoal("First");
+      saveMissionGoal("Second");
+      expect(getMissionGoal()).toBe("Second");
+    });
+  });
+
+  describe("Storage keys are independent", () => {
+    it("planning and subtask do not interfere", () => {
+      savePlanningDescription("planning desc");
+      saveSubtaskDescription("subtask desc");
+      expect(getPlanningDescription()).toBe("planning desc");
+      expect(getSubtaskDescription()).toBe("subtask desc");
+    });
+
+    it("planning and mission do not interfere", () => {
+      savePlanningDescription("planning desc");
+      saveMissionGoal("mission goal");
+      expect(getPlanningDescription()).toBe("planning desc");
+      expect(getMissionGoal()).toBe("mission goal");
+    });
+
+    it("subtask and mission do not interfere", () => {
+      saveSubtaskDescription("subtask desc");
+      saveMissionGoal("mission goal");
+      expect(getSubtaskDescription()).toBe("subtask desc");
+      expect(getMissionGoal()).toBe("mission goal");
+    });
+
+    it("clearing one does not affect others", () => {
+      savePlanningDescription("planning");
+      saveSubtaskDescription("subtask");
+      saveMissionGoal("mission");
+
+      clearSubtaskDescription();
+      expect(getPlanningDescription()).toBe("planning");
+      expect(getSubtaskDescription()).toBe("");
+      expect(getMissionGoal()).toBe("mission");
+    });
+  });
+});