build: add biome formatter and linter

tests/close_error.test.ts

@@ -1,9 +1,20 @@
-import { expect, test, mock, beforeEach, afterEach, describe, spyOn } from "bun:test";
+import {
+  afterEach,
+  beforeEach,
+  describe,
+  expect,
+  mock,
+  spyOn,
+  test,
+} from "bun:test";
 import * as os from "node:os";
 import { closeMultiModel } from "../src/core/close";
 
-let originalBun$: typeof Bun.$ = (globalThis as any).Bun?.$;
-let mockCommandResponses: Record<string, { ok: boolean; stdout: string; stderr: string }> = {};
+const originalBun$: typeof Bun.$ = (globalThis as any).Bun?.$;
+let mockCommandResponses: Record<
+  string,
+  { ok: boolean; stdout: string; stderr: string }
+> = {};
 let executedCommands: string[] = [];
 
 function setupMockBun$() {
@@ -15,7 +26,11 @@ function setupMockBun$() {
     if (cmd === "git worktree list --porcelain") {
       throw new Error("unexpected error");
     }
-    const response = mockCommandResponses[cmd] ?? { ok: true, stdout: "", stderr: "" };
+    const response = mockCommandResponses[cmd] ?? {
+      ok: true,
+      stdout: "",
+      stderr: "",
+    };
     return {
       quiet: () => ({
         nothrow: async () => ({
@@ -46,7 +61,11 @@ describe("closeMultiModel unexpected error handling", () => {
   });
 
   test("catches thrown error and returns failure", async () => {
-    const result = await closeMultiModel({ sessionName: "any-session", cleanupWorktrees: false, force: false });
+    const result = await closeMultiModel({
+      sessionName: "any-session",
+      cleanupWorktrees: false,
+      force: false,
+    });
     expect(result.success).toBe(false);
     expect(result.error).toContain("unexpected error");
   });