test(cmd/orca): smoke test ≥50% toe-hold, main→run refactor (T01.11, REQ-057)

Refactor main() into run() int (main calls os.Exit(run())) so the test
can exercise the CLI directly without os.Exit terminating the test
process. Add main_test.go with two cases: run() success path (version
command → exit 0) and run() error path (job run with missing spec →
exit 1, stderr contains "error:"). Low-effort toe-hold per RESEARCH
§1.1/§1.4 — do not over-invest in glue-code coverage.

Coverage: go test -cover ./cmd/orca → 80.0% (was 0%, target ≥50%).
go test -race PASS.

---ci---
project: orca
phase: 1
milestone: v0.8
status: execute
---/ci---

cmd/orca/main.go

@@ -8,8 +8,16 @@ import (
 )
 
 func main() {
+	os.Exit(run())
+}
+
+// run executes the orca CLI and returns the process exit code. It is
+// extracted from main so tests can exercise the error path without
+// os.Exit terminating the test process.
+func run() int {
 	if err := cli.Execute(); err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)
-		os.Exit(1)
+		return 1
 	}
+	return 0
 }

cmd/orca/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"io"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestRunSuccess(t *testing.T) {
+	orig := os.Args
+	t.Cleanup(func() { os.Args = orig })
+	os.Args = []string{"orca", "version"}
+	if code := run(); code != 0 {
+		t.Errorf("run() = %d, want 0", code)
+	}
+}
+
+func TestRunError(t *testing.T) {
+	origArgs := os.Args
+	t.Cleanup(func() { os.Args = origArgs })
+	os.Args = []string{"orca", "job", "run", "/nonexistent/spec.hcl"}
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	origStderr := os.Stderr
+	os.Stderr = w
+	t.Cleanup(func() { os.Stderr = origStderr })
+
+	code := run()
+	w.Close()
+	out, _ := io.ReadAll(r)
+	if code != 1 {
+		t.Errorf("run() = %d, want 1", code)
+	}
+	if !strings.Contains(string(out), "error:") {
+		t.Errorf("stderr missing 'error:' prefix: %s", out)
+	}
+}