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/entry_test.go

@@ -694,6 +694,33 @@ func TestCheckCommandWithSizeMismatch(t *testing.T) {
 		"check should have failed for size mismatch")
 }
 
+// TestCheckQuietShowsFailedFiles asserts that check -q prints nothing for a
+// tree that passes and still names each file that fails: --quiet hides
+// everything except errors, and a failed file is an error.
+func TestCheckQuietShowsFailedFiles(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	require.NoError(t, fs.MkdirAll(testDir, 0o755))
+	writeTestFile(t, fs, testFile1, "hello world")
+
+	opts := testOpts([]string{testApp, cmdGenerate, "-q", "-o", testManifest, testDir}, fs)
+	require.Equal(t, 0, runCLI(opts), "generate failed: %s", testStderr(t, opts))
+
+	args := []string{testApp, cmdCheck, "-q", testFlagBase, testDir, testManifest}
+
+	opts = testOpts(args, fs)
+	require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
+	assert.Empty(t, testStdout(t, opts))
+	assert.Empty(t, testStderr(t, opts))
+
+	writeTestFile(t, fs, testFile1, "HELLO WORLD")
+
+	opts = testOpts(args, fs)
+	assert.Equal(t, 1, runCLI(opts))
+	assert.Contains(t, testStderr(t, opts), "HASH_MISMATCH: file1.txt")
+}
+
 func TestBannerOutput(t *testing.T) {
 	t.Parallel()
 
@@ -926,8 +953,9 @@ func TestCheckWarnsAboutUnlistedFiles(t *testing.T) {
 			assert.Equal(t, 1, exitCode, "stderr: %s", stderr)
 			assert.Contains(t, stderr, unlisted)
 
-			exitCode, _ = check("-q", testFlagNoExtra)
+			exitCode, stderr = check("-q", testFlagNoExtra)
 			assert.Equal(t, 1, exitCode)
+			assert.Contains(t, stderr, unlisted)
 		})
 	}
 }