test(#146): add TestMainSubprocess_InvalidDocMapPath and TestMainSubprocess_InvalidDocMapFile

Move --doc-map path validation earlier in main() (before network I/O)
so subprocess tests can exercise both error paths:
- Path traversal: ../../../etc/passwd → 'resolves outside workspace'
- Nonexistent file: nonexistent.yml → 'failed to resolve doc-map'

Both tests follow the existing TEST_SUBPROCESS_MAIN=1 env gate pattern.

Closes #146

cmd/review-bot/main.go

@@ -173,6 +173,14 @@ func main() {
 		os.Exit(1)
 	}
 
+	// Early validation of filesystem-path flags (fail fast before network I/O)
+	if *docMapFile != "" {
+		if _, err := validateWorkspacePath(*docMapFile, "doc-map"); err != nil {
+			slog.Error("invalid doc-map path", "error", err)
+			os.Exit(1)
+		}
+	}
+
 	// Initialize clients
 	// Detect VCS type: explicit flag > env var > URL heuristic (default: gitea).
 	vcsType := envOrDefault("VCS_TYPE", "")

cmd/review-bot/main_test.go

@@ -1506,3 +1506,77 @@ func TestMainSubprocess_DeprecatedGiteaURLEnv(t *testing.T) {
 		t.Errorf("expected deprecation warning for GITEA_URL, got: %s", out)
 	}
 }
+
+// TestMainSubprocess_InvalidDocMapPath confirms that --doc-map with a path traversal
+// attempt is rejected before any network I/O.
+func TestMainSubprocess_InvalidDocMapPath(t *testing.T) {
+	if os.Getenv("TEST_SUBPROCESS_MAIN") == "1" {
+		flag.CommandLine = flag.NewFlagSet(os.Args[0], flag.ExitOnError)
+		os.Args = []string{"review-bot",
+			"--vcs-url", "https://gitea.example.com",
+			"--repo", "owner/repo",
+			"--pr", "1",
+			"--reviewer-token", "tok",
+			"--llm-base-url", "https://api.example.com",
+			"--llm-api-key", "key",
+			"--llm-model", "gpt-4",
+			"--doc-map", "../../../etc/passwd",
+		}
+		main()
+		return
+	}
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestMainSubprocess_InvalidDocMapPath")
+	cmd.Env = append(cleanEnv(),
+		"TEST_SUBPROCESS_MAIN=1",
+		"GITHUB_WORKSPACE="+t.TempDir(),
+	)
+	out, err := cmd.CombinedOutput()
+	if err == nil {
+		t.Fatal("expected non-zero exit with path traversal doc-map, got success")
+	}
+	output := string(out)
+	if !strings.Contains(output, "doc-map") {
+		t.Errorf("expected error mentioning doc-map, got: %s", output)
+	}
+	if !strings.Contains(output, "resolves outside workspace") {
+		t.Errorf("expected error about path traversal, got: %s", output)
+	}
+}
+
+// TestMainSubprocess_InvalidDocMapFile confirms that --doc-map with a nonexistent file
+// is rejected before any network I/O.
+func TestMainSubprocess_InvalidDocMapFile(t *testing.T) {
+	if os.Getenv("TEST_SUBPROCESS_MAIN") == "1" {
+		flag.CommandLine = flag.NewFlagSet(os.Args[0], flag.ExitOnError)
+		os.Args = []string{"review-bot",
+			"--vcs-url", "https://gitea.example.com",
+			"--repo", "owner/repo",
+			"--pr", "1",
+			"--reviewer-token", "tok",
+			"--llm-base-url", "https://api.example.com",
+			"--llm-api-key", "key",
+			"--llm-model", "gpt-4",
+			"--doc-map", "nonexistent.yml",
+		}
+		main()
+		return
+	}
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestMainSubprocess_InvalidDocMapFile")
+	cmd.Env = append(cleanEnv(),
+		"TEST_SUBPROCESS_MAIN=1",
+		"GITHUB_WORKSPACE="+t.TempDir(),
+	)
+	out, err := cmd.CombinedOutput()
+	if err == nil {
+		t.Fatal("expected non-zero exit with nonexistent doc-map file, got success")
+	}
+	output := string(out)
+	if !strings.Contains(output, "doc-map") {
+		t.Errorf("expected error mentioning doc-map, got: %s", output)
+	}
+	if !strings.Contains(output, "failed to resolve") {
+		t.Errorf("expected error about failed resolution, got: %s", output)
+	}
+}