Harden inbox JSON validation and claim conflicts

internal/cli/inbox/integration_test.go

@@ -608,14 +608,28 @@ func TestInboxJSONErrorsAndExitCodes(t *testing.T) {
 		"send",
 		"--from", "leader",
 		"--to", "worker-z",
-		"--subject", "Invalid body flags",
-		"--body", "inline",
-		"--body-file", filepath.Join(t.TempDir(), "missing.md"),
+		"--subject", "Invalid payload json",
+		"--payload-json", "not-json",
 	)
 	if exitCode != 30 {
 		t.Fatalf("expected invalid input exit code 30, got %d", exitCode)
 	}
 	assertErrorJSON(t, stdout, "invalid_input")
+
+	stdout, _, exitCode = executeInboxCommand(
+		"--db", dbPath,
+		"--json",
+		"send",
+		"--from", "leader",
+		"--to", "worker-z",
+		"--subject", "Invalid artifact json",
+		"--artifact", "/tmp/report.md",
+		"--artifact-metadata-json", "not-json",
+	)
+	if exitCode != 30 {
+		t.Fatalf("expected invalid artifact metadata exit code 30, got %d", exitCode)
+	}
+	assertErrorJSON(t, stdout, "invalid_input")
 }
 
 func runInboxCommand(t *testing.T, args ...string) string {