feat(KB-336): rename data directory from .kb to .fusion

- Rename data directory from .kb to .fusion across core, CLI, dashboard, and engine
- Update all path references in source files, tests, and CLI output
- Remove deprecated central-core infrastructure (central-core, central-db, central-integration)
- Remove obsolete test files (PlanningModeModal.test.tsx, ScheduleForm.test.tsx)
- Add changeset for the directory rename breaking change

packages/dashboard/app/components/SettingsModal.tsx

@@ -14,7 +14,7 @@ import { applyPresetToSelection, generatePresetId, validatePresetId } from "../u
  * Each section groups related settings fields under a sidebar nav item.
  * Sections have a `scope` to indicate where their settings are stored:
  *   - "global": User-level settings stored in ~/.pi/kb/settings.json (shared across projects)
- *   - "project": Project-specific settings stored in .kb/config.json
+ *   - "project": Project-specific settings stored in .fusion/config.json
  *   - undefined: Section operates independently of settings storage (e.g. authentication)
  *
  * To add a new section:
@@ -1256,8 +1256,8 @@ export function SettingsModal({
               <input
                 id="autoBackupDir"
                 type="text"
-                placeholder=".kb/backups"
-                value={form.autoBackupDir || ".kb/backups"}
+                placeholder=".fusion/backups"
+                value={form.autoBackupDir || ".fusion/backups"}
                 onChange={(e) =>
                   setForm((f) => ({ ...f, autoBackupDir: e.target.value }))
                 }

packages/dashboard/src/__tests__/file-service.test.ts

@@ -455,7 +455,7 @@ describe("task file operations", () => {
       await readFile(mockStore, "FN-123", "PROMPT.md");
 
       expect(mockReadFile).toHaveBeenCalledWith(
-        "/project/.kb/tasks/KB-123/PROMPT.md",
+        "/project/.fusion/tasks/KB-123/PROMPT.md",
         "utf-8",
       );
     });
@@ -476,7 +476,7 @@ describe("task file operations", () => {
       await readFile(mockStore, "FN-123", "PROMPT.md");
 
       expect(mockReadFile).toHaveBeenCalledWith(
-        "/project/.kb/tasks/KB-123/PROMPT.md",
+        "/project/.fusion/tasks/KB-123/PROMPT.md",
         "utf-8",
       );
     });
@@ -597,7 +597,7 @@ describe("workspace operations", () => {
 
       expect(result.content).toBe("Task description");
       expect(mockReadFile).toHaveBeenCalledWith(
-        "/project/.kb/tasks/KB-123/PROMPT.md",
+        "/project/.fusion/tasks/KB-123/PROMPT.md",
         "utf-8",
       );
     });
@@ -641,7 +641,7 @@ describe("workspace operations", () => {
 
       expect(result.success).toBe(true);
       expect(mockWriteFile).toHaveBeenCalledWith(
-        "/project/.kb/tasks/KB-123/output.txt",
+        "/project/.fusion/tasks/KB-123/output.txt",
         "Task output",
         "utf-8",
       );

packages/dashboard/src/file-service.ts

@@ -96,7 +96,7 @@ async function getTaskBasePath(store: TaskStore, taskId: string): Promise<string
     }
     // Fall back to task directory
     const rootDir = store.getRootDir();
-    return resolve(join(rootDir, ".kb", "tasks", taskId));
+    return resolve(join(rootDir, ".fusion", "tasks", taskId));
   } catch (err: any) {
     if (err.code === "ENOENT" || err.message?.includes("not found")) {
       throw new FileServiceError(`Task ${taskId} not found`, "ENOTASK");

packages/dashboard/src/routes.ts

@@ -1949,7 +1949,7 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
       // Remove PROMPT.md to force regeneration
       const { rm } = await import("node:fs/promises");
       const { join } = await import("node:path");
-      const promptPath = join(store.getRootDir(), ".kb", "tasks", task.id, "PROMPT.md");
+      const promptPath = join(store.getRootDir(), ".fusion", "tasks", task.id, "PROMPT.md");
       await rm(promptPath, { force: true });
 
       const updated = await store.getTask(task.id);