fix: use POSIX-compatible shell syntax in claude executor tests

Replace bash-only ${@: -1} with POSIX echo "$@" so tests pass
on dash (default /bin/sh on Ubuntu CI).

Author: bdougie

pkg/worker/claude_test.go

@@ -52,7 +52,7 @@ func TestClaudeExecutorUsesTaskPrompt(t *testing.T) {
 	fakeClaude := filepath.Join(dir, "claude")
 	// Script echoes the prompt argument (last arg) so we can verify it
 	// Args: --print --allowedTools <tools> <prompt>
-	if err := os.WriteFile(fakeClaude, []byte("#!/bin/sh\necho \"${@: -1}\""), 0o755); err != nil {
+	if err := os.WriteFile(fakeClaude, []byte("#!/bin/sh\necho \"$@\""), 0o755); err != nil {
 		t.Fatal(err)
 	}
 	t.Setenv("PATH", dir)
@@ -79,7 +79,7 @@ func TestClaudeExecutorUsesTaskPrompt(t *testing.T) {
 func TestClaudeExecutorFallsBackToBuildPrompt(t *testing.T) {
 	dir := t.TempDir()
 	fakeClaude := filepath.Join(dir, "claude")
-	if err := os.WriteFile(fakeClaude, []byte("#!/bin/sh\necho \"${@: -1}\""), 0o755); err != nil {
+	if err := os.WriteFile(fakeClaude, []byte("#!/bin/sh\necho \"$@\""), 0o755); err != nil {
 		t.Fatal(err)
 	}
 	t.Setenv("PATH", dir)