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/checker/checker.go

@@ -16,21 +16,21 @@ import (
 
 // Result represents the outcome of checking a single file.
 type Result struct {
-	Path    string
-	Status  Status
-	Message string
+	Path    string // Relative path from manifest
+	Status  Status // Verification result status
+	Message string // Human-readable description of the result
 }
 
 // Status represents the verification status of a file.
 type Status int
 
 const (
-	StatusOK Status = iota
-	StatusMissing
-	StatusSizeMismatch
-	StatusHashMismatch
-	StatusExtra // File exists on disk but not in manifest
-	StatusError
+	StatusOK           Status = iota // File matches manifest (size and hash verified)
+	StatusMissing                    // File not found on disk
+	StatusSizeMismatch               // File size differs from manifest
+	StatusHashMismatch               // File hash differs from manifest
+	StatusExtra                      // File exists on disk but not in manifest
+	StatusError                      // Error occurred during verification
 )
 
 func (s Status) String() string {
@@ -54,12 +54,12 @@ func (s Status) String() string {
 
 // CheckStatus contains progress information for the check operation.
 type CheckStatus struct {
-	TotalFiles   int64
-	CheckedFiles int64
-	TotalBytes   int64
-	CheckedBytes int64
-	BytesPerSec  float64
-	Failures     int64
+	TotalFiles   int64   // Total number of files in manifest
+	CheckedFiles int64   // Number of files checked so far
+	TotalBytes   int64   // Total bytes to verify (sum of all file sizes)
+	CheckedBytes int64   // Bytes verified so far
+	BytesPerSec  float64 // Current throughput rate
+	Failures     int64   // Number of verification failures encountered
 }
 
 // Checker verifies files against a manifest.