Fix exit codes, 100MB truncation, go.mod, minor robustness

Exit codes:
- SetFlagErrorFunc wraps cobra flag errors as UsageError (exit 2)
- isCobraUsageError detects arg-count and unknown-command errors (exit 2)
- Both now emit code=usage_error in JSON instead of api_error

API client:
- Detect 100MB truncation and return clear ApiError instead of letting
  downstream JSON parsing fail with cryptic 'unexpected end of JSON input'

config_unix.go:
- Check partial write: return error if fewer bytes written than expected

errors_test.go:
- Use comma-ok type assertion to give clearer failure message

go.mod:
- go mod tidy: briandowns/spinner and tidwall/pretty no longer // indirect

homebrew-tap formula:
- Inject version via ldflags -X .../pkg/version.Version=#{version}
  so installs show the actual version instead of 'dev'

Author: ilyazub

go.mod

@@ -4,19 +4,19 @@ go 1.25.0
 
 require (
 	github.com/BurntSushi/toml v1.6.0
+	github.com/briandowns/spinner v1.23.2
 	github.com/itchyny/gojq v0.12.18
 	github.com/spf13/cobra v1.10.2
+	github.com/tidwall/pretty v1.2.1
 	golang.org/x/term v0.41.0
 )
 
 require (
-	github.com/briandowns/spinner v1.23.2 // indirect
 	github.com/fatih/color v1.7.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/itchyny/timefmt-go v0.1.7 // indirect
 	github.com/mattn/go-colorable v0.1.2 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
-	github.com/tidwall/pretty v1.2.1 // indirect
 	golang.org/x/sys v0.42.0 // indirect
 )

pkg/api/client.go

@@ -59,10 +59,14 @@ func (c *Client) doGet(endpoint string, params map[string]string) ([]byte, error
 	}
 	defer resp.Body.Close()
 
-	body, err := io.ReadAll(io.LimitReader(resp.Body, 100<<20)) // 100 MB limit
+	const maxBytes = 100 << 20 // 100 MB
+	body, err := io.ReadAll(io.LimitReader(resp.Body, maxBytes))
 	if err != nil {
 		return nil, &clierrors.NetworkError{Message: "Failed to read response: " + err.Error()}
 	}
+	if len(body) == maxBytes {
+		return nil, &clierrors.ApiError{Message: "Response exceeded 100 MB limit"}
+	}
 
 	if resp.StatusCode != http.StatusOK {
 		// Try to extract error message from JSON body

pkg/cmd/root.go

@@ -47,6 +47,11 @@ func init() {
 	rootCmd.PersistentFlags().StringVar(&apiKeyFlag, "api-key", "", "SerpApi API key (env: SERPAPI_KEY)")
 	rootCmd.PersistentFlags().StringVar(&fieldsFlag, "fields", "", "Restrict JSON fields (server-side json_restrictor)")
 	rootCmd.PersistentFlags().StringVar(&jqFlag, "jq", "", "Apply jq filter to output")
+
+	// Wrap cobra flag-parsing errors as UsageError so they get exit code 2.
+	rootCmd.SetFlagErrorFunc(func(_ *cobra.Command, err error) error {
+		return &clierrors.UsageError{Message: err.Error()}
+	})
 }
 
 // resolveAPIKey merges --api-key flag with SERPAPI_KEY env var, then config file.

pkg/config/config_unix.go

@@ -3,6 +3,7 @@
 package config
 
 import (
+	"fmt"
 	"os"
 )
 
@@ -16,6 +17,12 @@ func writeFileSecure(path string, data []byte) error {
 		return err
 	}
 	defer f.Close()
-	_, err = f.Write(data)
-	return err
+	n, err := f.Write(data)
+	if err != nil {
+		return err
+	}
+	if n != len(data) {
+		return fmt.Errorf("incomplete write: wrote %d of %d bytes", n, len(data))
+	}
+	return nil
 }

pkg/errors/errors.go

@@ -33,6 +33,9 @@ func ExitCode(err error) int {
 	case *NetworkError:
 		return 1
 	default:
+		if isCobraUsageError(err) {
+			return 2
+		}
 		return 1
 	}
 }
@@ -46,10 +49,21 @@ func errorCode(err error) string {
 	case *NetworkError:
 		return "network_error"
 	default:
+		if isCobraUsageError(err) {
+			return "usage_error"
+		}
 		return "api_error"
 	}
 }
 
+// isCobraUsageError detects cobra argument-validation errors by message pattern.
+func isCobraUsageError(err error) bool {
+	msg := err.Error()
+	return strings.HasPrefix(msg, "accepts ") ||
+		strings.HasPrefix(msg, "unknown command") ||
+		strings.HasPrefix(msg, "required flag")
+}
+
 // PrintError writes a structured JSON error to stderr.
 func PrintError(err error) {
 	code := errorCode(err)

pkg/errors/errors_test.go

@@ -73,7 +73,10 @@ func TestPrintErrorUsageError(t *testing.T) {
 	if err := json.Unmarshal([]byte(output), &parsed); err != nil {
 		t.Fatalf("failed to parse error JSON: %v\noutput: %s", err, output)
 	}
-	errObj := parsed["error"].(map[string]any)
+	errObj, ok := parsed["error"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected error object, got %T", parsed["error"])
+	}
 	if errObj["code"] != "usage_error" {
 		t.Errorf("expected code usage_error, got %v", errObj["code"])
 	}