fix: Handle push to checked-out branch in local non-bare repos

git refuses to push to a branch that is currently checked out in a
non-bare repository. When the clone's origin is the user's local repo,
this blocks merge_and_push entirely.

On "branch is currently checked out" error, temporarily set
receive.denyCurrentBranch=updateInstead on the remote and retry.
This uses git's built-in mechanism to update the working tree safely
(rejects if dirty).

apps/server/git/simple-git-branch-manager.ts

@@ -6,7 +6,7 @@
  * on project clones without requiring a worktree.
  */
 
-import { join } from 'node:path';
+import { join, resolve } from 'node:path';
 import { mkdtempSync, rmSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { simpleGit } from 'simple-git';
@@ -164,7 +164,26 @@ export class SimpleGitBranchManager implements BranchManager {
 
   async pushBranch(repoPath: string, branch: string, remote = 'origin'): Promise<void> {
     const git = simpleGit(repoPath);
+    try {
       await git.push(remote, branch);
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : String(err);
+      if (!msg.includes('branch is currently checked out')) throw err;
+
+      // Local non-bare repo with the branch checked out — temporarily allow it.
+      // receive.denyCurrentBranch=updateInstead updates the remote's working tree
+      // and index to match, or rejects if the working tree is dirty.
+      const remoteUrl = (await git.remote(['get-url', remote]))?.trim();
+      if (!remoteUrl) throw err;
+      const remotePath = resolve(repoPath, remoteUrl);
+      const remoteGit = simpleGit(remotePath);
+      await remoteGit.addConfig('receive.denyCurrentBranch', 'updateInstead');
+      try {
+        await git.push(remote, branch);
+      } finally {
+        await remoteGit.raw(['config', '--unset', 'receive.denyCurrentBranch']);
+      }
+    }
     log.info({ repoPath, branch, remote }, 'branch pushed to remote');
   }