Add Verbose log level between Info and Debug

Implemented full log level hierarchy: Fatal, Error, Warn, Info, Verbose, Debug.
- Verbose level (-v) shows detailed operations like file changes (M/A/D)
- Debug level (-vv) shows low-level tracing with caller info
- Quiet mode (-q) sets level to Error, suppressing Info messages
- Banner and summary output now use log levels for filtering

internal/cli/entry_test.go

@@ -173,10 +173,10 @@ func TestBannerOutput(t *testing.T) {
 	exitCode := RunWithOptions(opts)
 	assert.Equal(t, 0, exitCode)
 
-	// Banner ASCII art should be in stdout
-	stdout := opts.Stdout.(*bytes.Buffer).String()
-	assert.Contains(t, stdout, "___")
-	assert.Contains(t, stdout, "\\")
+	// Banner ASCII art should be in stderr (via log.Info)
+	stderr := opts.Stderr.(*bytes.Buffer).String()
+	assert.Contains(t, stderr, "___")
+	assert.Contains(t, stderr, "\\")
 }
 
 func TestUnknownCommand(t *testing.T) {