Re-vendor the shared files from sneak/prompts at 0653579 (closes #52)

Takes .golangci.yml, .dockerignore, .gitignore, .editorconfig, the
workflow and REPO_POLICIES.md from sneak/prompts 0653579, with this
repository's own entries after the shared content. Lint (golangci-lint
v2.14.0) and test are Dockerfile phases that script/lint and script/test
build alone with a new CACHEBUST value, keeping Go's and golangci-lint's
caches; the image build depends on both. make fmt and make fmt-check also
format the markdown with prettier, pinned in yarn.lock. The agent
guidance moves to AGENTS.md. The Go code is fixed for what the new
configuration finds, and the AS and prefix detail reads now return the
rows' error after their loops.

Model: opus-5-5

internal/config/config.go

@@ -2,6 +2,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -27,6 +28,12 @@ const (
 	maxPort = 65535
 )
 
+var (
+	errRelativeXDGDataHome = errors.New("XDG_DATA_HOME must be an absolute path")
+	errUnsupportedOS       = errors.New("unsupported operating system")
+	errInvalidPort         = errors.New("PORT must be a whole number")
+)
+
 // Config holds configuration for the entire application
 type Config struct {
 	// StateDir is the directory for all application state (database, snapshots)
@@ -38,11 +45,14 @@ type Config struct {
 	// MaxRuntime is the maximum runtime (0 = run forever)
 	MaxRuntime time.Duration
 
-	// EnableBatchedDatabaseWrites enables batched database operations for better performance
+	// EnableBatchedDatabaseWrites enables batched database operations for
+	// better performance
 	EnableBatchedDatabaseWrites bool
 
-	// RouteExpirationTimeout is how long a route can go without being refreshed before expiring
-	// Default is 2 hours which is conservative for BGP (typical BGP hold time is 90-180 seconds)
+	// RouteExpirationTimeout is how long a route can go without being
+	// refreshed before expiring
+	// Default is 2 hours which is conservative for BGP (typical BGP hold
+	// time is 90-180 seconds)
 	RouteExpirationTimeout time.Duration
 }
 
@@ -59,11 +69,14 @@ func New() (*Config, error) {
 	}
 
 	return &Config{
-		StateDir:                    stateDir,
-		Port:                        port,
-		MaxRuntime:                  0,                                           // Run forever by default
-		EnableBatchedDatabaseWrites: true,                                        // Enable batching by default
-		RouteExpirationTimeout:      defaultRouteExpirationMinutes * time.Minute, // For active route monitoring
+		StateDir: stateDir,
+		Port:     port,
+		// Run forever by default
+		MaxRuntime: 0,
+		// Enable batching by default
+		EnableBatchedDatabaseWrites: true,
+		// For active route monitoring
+		RouteExpirationTimeout: defaultRouteExpirationMinutes * time.Minute,
 	}, nil
 }
 
@@ -89,7 +102,7 @@ func getStateDirectory() (string, error) {
 		// the database somewhere unexpected.
 		xdgData := os.Getenv("XDG_DATA_HOME")
 		if xdgData != "" && !filepath.IsAbs(xdgData) {
-			return "", fmt.Errorf("XDG_DATA_HOME must be an absolute path, got %q", xdgData)
+			return "", fmt.Errorf("%w, got %q", errRelativeXDGDataHome, xdgData)
 		}
 
 		// Unix-like: /var/lib/berlin.sneak.app.routewatch if root, else XDG_DATA_HOME
@@ -111,7 +124,7 @@ func getStateDirectory() (string, error) {
 		return filepath.Join(home, ".local", "share", AppIdentifier), nil
 
 	default:
-		return "", fmt.Errorf("unsupported operating system: %s", runtime.GOOS)
+		return "", fmt.Errorf("%w: %s", errUnsupportedOS, runtime.GOOS)
 	}
 }
 
@@ -125,7 +138,8 @@ func getPort() (int, error) {
 	// ParseUint, unlike Atoi, refuses a sign: the health check URL cannot use "+9090"
 	port, err := strconv.ParseUint(value, 10, 0)
 	if err != nil || port < 1 || port > maxPort {
-		return 0, fmt.Errorf("PORT must be a whole number from 1 to %d, got %q", maxPort, value)
+		return 0, fmt.Errorf("%w from 1 to %d, got %q",
+			errInvalidPort, maxPort, value)
 	}
 
 	return int(port), nil
@@ -134,7 +148,8 @@ func getPort() (int, error) {
 // EnsureDirectories creates all necessary directories if they don't exist
 func (c *Config) EnsureDirectories() error {
 	// Ensure state directory exists
-	if err := os.MkdirAll(c.StateDir, dirPermissions); err != nil {
+	err := os.MkdirAll(c.StateDir, dirPermissions)
+	if err != nil {
 		return fmt.Errorf("failed to create state directory: %w", err)
 	}
 

internal/config/config_internal_test.go

@@ -36,7 +36,8 @@ func TestNewRefusesInvalidPort(t *testing.T) {
 			t.Setenv("PORT", value)
 			t.Setenv("XDG_DATA_HOME", "")
 
-			if _, err := New(); err == nil {
+			_, err := New()
+			if err == nil {
 				t.Errorf("New() with PORT=%q returned no error", value)
 			}
 		})
@@ -51,12 +52,16 @@ func TestNewRefusesRelativeXDGDataHome(t *testing.T) {
 	t.Setenv("PORT", "")
 
 	t.Setenv("XDG_DATA_HOME", "relative/path")
-	if _, err := New(); err == nil {
+
+	_, err := New()
+	if err == nil {
 		t.Error("New() with a relative XDG_DATA_HOME returned no error")
 	}
 
 	t.Setenv("XDG_DATA_HOME", "/var/lib")
-	if _, err := New(); err != nil {
+
+	_, err = New()
+	if err != nil {
 		t.Errorf("New() with XDG_DATA_HOME=/var/lib: %v", err)
 	}
 }