Log failed files at error level so check -q shows them (closes #195)

check logged each failed file at info level, and -q shows errors only,
so `check -q` reported a failure through its exit status alone. Each
failed file, and each file the manifest does not list under
--no-extra-files, is now logged at error level. A file the manifest
does not list stays a warning without --no-extra-files, and the closing
summary stays at info level.

Model: opus-5-5

internal/cli/check.go

@@ -189,8 +189,8 @@ func reportCheckProgress(progress <-chan mfer.CheckStatus, wg *sync.WaitGroup) {
 	log.ProgressDone()
 }
 
-// countCheckFailures consumes check results, counting and logging
-// failures, then closes done.
+// countCheckFailures consumes check results, counting failures and logging
+// each at error level so that --quiet still shows them, then closes done.
 func countCheckFailures(
 	results <-chan mfer.Result, failures *int64, done chan<- struct{},
 ) {
@@ -198,7 +198,7 @@ func countCheckFailures(
 		if result.Status != mfer.StatusOK {
 			*failures++
 
-			log.Infof("%s: %s (%s)", result.Status, result.Path, result.Message)
+			log.Errorf("%s: %s (%s)", result.Status, result.Path, result.Message)
 		} else {
 			log.Verbosef("%s: %s", result.Status, result.Path)
 		}
@@ -208,8 +208,8 @@ func countCheckFailures(
 }
 
 // findExtraFiles reports files present on disk but absent from the
-// manifest, and anything the search cannot read: each is a failure under
-// --no-extra-files, otherwise a warning.
+// manifest, and anything the search cannot read: each is a failure, logged
+// at error level, under --no-extra-files, otherwise a warning.
 func findExtraFiles(
 	ctx context.Context, cmd *cli.Command, chk *mfer.Checker, failures *int64,
 ) error {
@@ -221,7 +221,7 @@ func findExtraFiles(
 			if cmd.Bool("no-extra-files") {
 				*failures++
 
-				log.Infof("%s: %s (%s)", result.Status, result.Path, result.Message)
+				log.Errorf("%s: %s (%s)", result.Status, result.Path, result.Message)
 			} else {
 				log.Warnf("%s: %s (%s)", result.Status, result.Path, result.Message)
 			}