Feat (RAG): tying tui calls to rag funcs [WIP; skip-ci]

RAG itself is annoying to properly implement, plucking sentences with no
context is useless. Also it should not be a part of main package, same
for goes for tui. The number of global vars is absurd.

pngmeta/metareader.go

@@ -103,6 +103,9 @@ func ReadDirCards(dirname, uname string) ([]*models.CharCard, error) {
 	}
 	resp := []*models.CharCard{}
 	for _, f := range files {
+		if f.IsDir() {
+			continue
+		}
 		if strings.HasSuffix(f.Name(), ".png") {
 			fpath := path.Join(dirname, f.Name())
 			cc, err := ReadCard(fpath, uname)