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/cli/src/bin.ts

@@ -28,7 +28,7 @@ if (isBunBinary) {
     writeFileSync(
       join(tmp, "package.json"),
       JSON.stringify(
-        { name: "kb", version: "0.1.0", type: "module", piConfig: { name: "kb", configDir: ".kb" } },
+        { name: "kb", version: "0.1.0", type: "module", piConfig: { name: "kb", configDir: ".fusion" } },
         null,
         2,
       ) + "\n",

packages/cli/src/commands/dashboard.ts

@@ -687,7 +687,7 @@ export async function runDashboard(port: number, opts: { paused?: boolean; dev?:
     console.log(`  ────────────────────────`);
     console.log(`  → http://localhost:${actualPort}`);
     console.log();
-    console.log(`  Tasks stored in .kb/tasks/`);
+    console.log(`  Tasks stored in .fusion/tasks/`);
     console.log(`  Merge:      AI-assisted (conflict resolution + commit messages)`);
     if (opts.dev) {
       console.log(`  AI engine:  ✗ disabled (dev mode)`);

packages/cli/src/commands/task.ts

@@ -43,7 +43,7 @@ export async function runTaskCreate(descriptionArg?: string, attachFiles?: strin
   if (task.dependencies.length > 0) {
     console.log(`    Dependencies: ${task.dependencies.join(", ")}`);
   }
-  console.log(`    Path:   .kb/tasks/${task.id}/`);
+  console.log(`    Path:   .fusion/tasks/${task.id}/`);
 
   if (attachFiles && attachFiles.length > 0) {
     const { readFile } = await import("node:fs/promises");
@@ -241,7 +241,7 @@ export async function runTaskLogs(id: string, options: LogsOptions = {}) {
   // Follow mode: watch for new entries
   if (options.follow) {
     const cwd = process.cwd();
-    const logPath = join(cwd, ".kb", "tasks", id, "agent.log");
+    const logPath = join(cwd, ".fusion", "tasks", id, "agent.log");
 
     if (!existsSync(logPath)) {
       console.log(`\n  Waiting for log file to be created...`);
@@ -434,7 +434,7 @@ export async function runTaskAttach(id: string, filePath: string) {
   console.log();
   console.log(`  ✓ Attached to ${id}: ${attachment.originalName}`);
   console.log(`    File: ${attachment.filename} (${sizeKB} KB)`);
-  console.log(`    Path: .kb/tasks/${id}/attachments/${attachment.filename}`);
+  console.log(`    Path: .fusion/tasks/${id}/attachments/${attachment.filename}`);
   console.log();
 }
 
@@ -477,7 +477,7 @@ export async function runTaskDuplicate(id: string) {
 
   console.log();
   console.log(`  ✓ Duplicated ${id} → ${newTask.id}`);
-  console.log(`    Path: .kb/tasks/${newTask.id}/`);
+  console.log(`    Path: .fusion/tasks/${newTask.id}/`);
   console.log();
 }
 
@@ -509,7 +509,7 @@ export async function runTaskRefine(id: string, feedbackArg?: string) {
   console.log(`  ✓ Created refinement ${newTask.id} for ${id}`);
   console.log(`    Column: triage`);
   console.log(`    Dependency: ${id}`);
-  console.log(`    Path: .kb/tasks/${newTask.id}/`);
+  console.log(`    Path: .fusion/tasks/${newTask.id}/`);
   console.log();
 }
 
@@ -1463,7 +1463,7 @@ export async function runTaskPlan(initialPlanArg?: string, yesFlag = false): Pro
           if (task.dependencies.length > 0) {
             console.log(`    Dependencies: ${task.dependencies.join(", ")}`);
           }
-          console.log(`    Path:   .kb/tasks/${task.id}/`);
+          console.log(`    Path:   .fusion/tasks/${task.id}/`);
           console.log();
         } else {
           console.log("\n  Task creation cancelled.\n");

packages/cli/src/extension.ts

@@ -99,7 +99,7 @@ export default function kbExtension(pi: ExtensionAPI) {
               (task.dependencies.length
                 ? `Dependencies: ${task.dependencies.join(", ")}\n`
                 : "") +
-              `Path: .kb/tasks/${task.id}/`,
+              `Path: .fusion/tasks/${task.id}/`,
           },
         ],
         details: { taskId: task.id, column: task.column, dependencies: task.dependencies },
@@ -287,7 +287,7 @@ export default function kbExtension(pi: ExtensionAPI) {
             type: "text",
             text:
               `Attached to ${params.id}: ${attachment.originalName} (${sizeKB} KB)\n` +
-              `Path: .kb/tasks/${params.id}/attachments/${attachment.filename}`,
+              `Path: .fusion/tasks/${params.id}/attachments/${attachment.filename}`,
           },
         ],
         details: { taskId: params.id, attachment },