clone時に既存ブランチのcheckoutが失敗する問題を修正

cloneAndIsolateがgit remote remove originした後、リモート追跡refが
全て消えるため、default以外の既存ブランチをcheckoutできなかった。

git clone --branchでclone時にローカルブランチを作成するように変更。
併せてブランチ名フォーマットからgit非互換の#を除去。

src/__tests__/branchList.regression.test.ts

@@ -46,7 +46,7 @@ function setupRepoForIssue167(options?: { disableReflog?: boolean; firstBranchCo
   writeAndCommit(repoDir, 'develop-takt.txt', 'develop takt\n', 'takt: old instruction on develop');
   writeAndCommit(repoDir, 'develop-b.txt', 'develop b\n', 'develop commit B');
 
-  const taktBranch = 'takt/#167/fix-original-instruction';
+  const taktBranch = 'takt/167/fix-original-instruction';
   runGit(repoDir, ['checkout', '-b', taktBranch]);
   const firstBranchCommitMessage = options?.firstBranchCommitMessage ?? 'takt: github-issue-167-fix-original-instruction';
   writeAndCommit(repoDir, 'task-1.txt', 'task1\n', firstBranchCommitMessage);

src/__tests__/clone.test.ts

@@ -207,7 +207,7 @@ describe('branch and worktree path formatting with issue numbers', () => {
     });
   }
 
-  it('should format branch as takt/#{issue}/{slug} when issue number is provided', () => {
+  it('should format branch as takt/{issue}/{slug} when issue number is provided', () => {
     // Given: issue number 99 with slug
     setupMockForPathTest();
 
@@ -219,7 +219,7 @@ describe('branch and worktree path formatting with issue numbers', () => {
     });
 
     // Then: branch should use issue format
-    expect(result.branch).toBe('takt/#99/fix-login-timeout');
+    expect(result.branch).toBe('takt/99/fix-login-timeout');
   });
 
   it('should format branch as takt/{timestamp}-{slug} when no issue number', () => {

src/infra/task/clone.ts

@@ -77,7 +77,7 @@ export class CloneManager {
     const slug = slugify(options.taskSlug);
 
     if (options.issueNumber !== undefined && slug) {
-      return `takt/#${options.issueNumber}/${slug}`;
+      return `takt/${options.issueNumber}/${slug}`;
     }
 
     const timestamp = CloneManager.generateTimestamp();
@@ -124,13 +124,24 @@ export class CloneManager {
     return projectDir;
   }
 
-  /** Clone a repository and remove origin to isolate from the main repo */
-  private static cloneAndIsolate(projectDir: string, clonePath: string): void {
+  /** Clone a repository and remove origin to isolate from the main repo.
+   *  When `branch` is specified, `--branch` is passed to `git clone` so the
+   *  branch is checked out as a local branch *before* origin is removed.
+   *  Without this, non-default branches are lost when `git remote remove origin`
+   *  deletes the remote-tracking refs.
+   */
+  private static cloneAndIsolate(projectDir: string, clonePath: string, branch?: string): void {
     const referenceRepo = CloneManager.resolveMainRepo(projectDir);
 
     fs.mkdirSync(path.dirname(clonePath), { recursive: true });
 
-    execFileSync('git', ['clone', '--reference', referenceRepo, '--dissociate', projectDir, clonePath], {
+    const cloneArgs = ['clone', '--reference', referenceRepo, '--dissociate'];
+    if (branch) {
+      cloneArgs.push('--branch', branch);
+    }
+    cloneArgs.push(projectDir, clonePath);
+
+    execFileSync('git', cloneArgs, {
       cwd: projectDir,
       stdio: 'pipe',
     });
@@ -174,11 +185,10 @@ export class CloneManager {
 
     log.info('Creating shared clone', { path: clonePath, branch });
 
-    CloneManager.cloneAndIsolate(projectDir, clonePath);
-
-    if (CloneManager.branchExists(clonePath, branch)) {
-      execFileSync('git', ['checkout', branch], { cwd: clonePath, stdio: 'pipe' });
+    if (CloneManager.branchExists(projectDir, branch)) {
+      CloneManager.cloneAndIsolate(projectDir, clonePath, branch);
     } else {
+      CloneManager.cloneAndIsolate(projectDir, clonePath);
       execFileSync('git', ['checkout', '-b', branch], { cwd: clonePath, stdio: 'pipe' });
     }
 
@@ -195,8 +205,7 @@ export class CloneManager {
 
     log.info('Creating temp clone for branch', { path: clonePath, branch });
 
-    CloneManager.cloneAndIsolate(projectDir, clonePath);
-    execFileSync('git', ['checkout', branch], { cwd: clonePath, stdio: 'pipe' });
+    CloneManager.cloneAndIsolate(projectDir, clonePath, branch);
 
     this.saveCloneMeta(projectDir, branch, clonePath);
     log.info('Temp clone created', { path: clonePath, branch });