fix(action): configure git user in worktree before commit

Worktrees don't inherit git config from main repo, causing 'git commit'
to fail with exit status 128 when user.name/user.email are not set.
Configure with poimen agent identity before each commit.

action/git.go

@@ -78,6 +78,11 @@ type GitCommitInput struct {
 
 // GitCommitActivity commits changes in a worktree.
 func GitCommitActivity(ctx context.Context, in GitCommitInput) error {
+	// Configure git user for commits if not already configured
+	// (worktrees don't inherit config from main repo)
+	exec.CommandContext(ctx, "git", "-C", in.WorktreePath, "config", "user.email", "[email protected]").Run()
+	exec.CommandContext(ctx, "git", "-C", in.WorktreePath, "config", "user.name", "Poimen Agent").Run()
+
 	// Stage all changes
 	cmd := exec.CommandContext(ctx, "git", "-C", in.WorktreePath, "add", "-A")
 	if err := cmd.Run(); err != nil {