Allow naming without an artist folder and per-folder naming rules

The artist folder can be left empty for Album/01 Title (no artist tag
needed), and folders such as Video Games can have their own formats.
Files in a rule folder are only renamed inside it; other files are never
moved into it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -105,6 +105,11 @@ use the folder image. A replaced `cover.jpg` goes to quarantine, and every chang
 **Organize (rename files from tags).** The *Organize* tab sets how files are named, in the style of Lidarr: an **artist folder**, an
 **album folder**, a **track format** and a separate **multi-disc track format**, with presets. The default is
 `{Artist Name}/{Album Title}/{track:00} {Track Title}`, and multi-disc albums get `{Medium Format} {medium:00}/…` → `Disc 01`, `Disc 02`.
+Leave the artist folder empty for `Album/01 Title`; songs then don't need an artist tag.
+
+**Folders with their own naming.** Part of a library can use different formats, such as game soundtracks in
+`Video Games/{Album Title}/{track:00} {Track Title}` while the rest stays `Artist/Album/01 Title`. Files inside such a folder are only
+renamed within it, and other files are never moved into it (they are skipped with a reason instead). Folder rules can't be nested.
 
 Tokens: `{Artist Name}`, `{Artist NameThe}` (The Beatles → Beatles, The), `{Artist CleanName}`, `{Artist NameFirstCharacter}`,
 `{Album Title}`, `{Album TitleThe}`, `{Album CleanTitle}`, `{Release Year}`, `{track:0}`/`{track:00}`, `{medium:0}`/`{medium:00}`,