Add godoc strings to all exported types, functions, and fields

Documents:
- cli: NO_COLOR, RunOptions fields, CLIApp, VersionString
- checker: Result fields, Status constants, CheckStatus fields
- scanner: EnumerateStatus, ScanStatus, Options, FileEntry fields
- log: Level alias, DisableStyling, Init, Info/Debug functions,
  verbosity helpers, GetLogger, GetLevel, WithError
- mfer: ManifestScanOptions, New, NewFromPaths, NewFromFS, MAGIC

internal/cli/entry.go

@@ -7,6 +7,8 @@ import (
 	"github.com/spf13/afero"
 )
 
+// NO_COLOR disables colored output when set. Automatically true if the
+// NO_COLOR environment variable is present (per https://no-color.org/).
 var NO_COLOR bool
 
 func init() {
@@ -17,15 +19,16 @@ func init() {
 }
 
 // RunOptions contains all configuration for running the CLI application.
+// Use DefaultRunOptions for standard CLI execution, or construct manually for testing.
 type RunOptions struct {
-	Appname string
-	Version string
-	Gitrev  string
-	Args    []string
-	Stdin   io.Reader
-	Stdout  io.Writer
-	Stderr  io.Writer
-	Fs      afero.Fs
+	Appname string    // Application name displayed in help and version output
+	Version string    // Version string (typically set at build time)
+	Gitrev  string    // Git revision hash (typically set at build time)
+	Args    []string  // Command-line arguments (typically os.Args)
+	Stdin   io.Reader // Standard input stream
+	Stdout  io.Writer // Standard output stream
+	Stderr  io.Writer // Standard error stream
+	Fs      afero.Fs  // Filesystem abstraction for file operations
 }
 
 // DefaultRunOptions returns RunOptions configured for normal CLI execution.

internal/cli/mfer.go

@@ -11,6 +11,8 @@ import (
 	"sneak.berlin/go/mfer/internal/log"
 )
 
+// CLIApp is the main CLI application container. It holds configuration,
+// I/O streams, and filesystem abstraction to enable testing and flexibility.
 type CLIApp struct {
 	appname     string
 	version     string
@@ -19,13 +21,10 @@ type CLIApp struct {
 	exitCode    int
 	app         *cli.App
 
-	// I/O streams - all program input/output should go through these
-	Stdin  io.Reader
-	Stdout io.Writer
-	Stderr io.Writer
-
-	// Fs is the filesystem abstraction - defaults to OsFs for real filesystem
-	Fs afero.Fs
+	Stdin  io.Reader // Standard input stream
+	Stdout io.Writer // Standard output stream for normal output
+	Stderr io.Writer // Standard error stream for diagnostics
+	Fs     afero.Fs  // Filesystem abstraction for all file operations
 }
 
 const banner = `
@@ -45,6 +44,7 @@ func (mfa *CLIApp) printBanner() {
 	fmt.Fprintln(mfa.Stdout, banner)
 }
 
+// VersionString returns the version and git revision formatted for display.
 func (mfa *CLIApp) VersionString() string {
 	return fmt.Sprintf("%s (%s)", mfa.version, mfa.gitrev)
 }