fix(organize): stop keyword-dump tags from becoming folder names (#1119)

CivitAI tags are normally short single-concept labels, but some uploaders
pack their entire keyword list into one tag. The model in #1119 carries
"lora, character, rosie, irish, ... face" as a single 181-character tag.
Priority resolution matches aliases by exact equality, so that tag matched
nothing and resolve_priority_tag_for_model fell back to tags[0] -- the blob.
With the default "{base_model}/{first_tag}" template the model was filed
under "Krea 2/<181-character blob>/", and the full path plus the
".civitai.info" sidecar and the preview images next to it ran into the
Windows MAX_PATH limit.

Tags also bypassed sanitization on the way into a path: both
calculate_relative_path_for_model and DownloadManager._calculate_relative_path
sanitized model_name and version_name but interpolated {first_tag} verbatim,
so a tag containing "/" or ":" silently produced nested or illegal folders.

Two changes:

- The fallback skips tags that cannot serve as a folder name.
  is_usable_path_tag rejects comma-separated keyword dumps and tags longer
  than MAX_PATH_TAG_LENGTH; the resolver returns "" when nothing usable is
  left, which callers already render as "no tags". Whole-tag priority
  matching is untouched, so existing priority configurations behave the
  same.
- sanitize_folder_name gains an optional max_length, and every tag-derived
  segment now goes through it. Tags are capped at MAX_PATH_TAG_LENGTH, model
  and version names at MAX_FOLDER_NAME_LENGTH, and rendered filename stems at
  MAX_FILENAME_STEM_LENGTH.

For the reported model the folder becomes "Krea 2/base model" instead of the
blob, and the full path drops from 235 to 64 characters.

Existing libraries are not migrated up front: a path is only recomputed on
download, on an auto-organize run or when a filename template is applied, and
values already inside the caps are left byte-identical. Models previously
filed under a keyword-dump folder move on the next auto-organize run.

py/services/settings_manager.py

@@ -47,6 +47,7 @@ from ..utils.settings_paths import (
 from ..utils.tag_priorities import (
     PriorityTagEntry,
     collect_canonical_tags,
+    is_usable_path_tag,
     parse_priority_tag_string,
     resolve_priority_tag,
 )
@@ -1569,9 +1570,12 @@ class SettingsManager:
         if resolved:
             return resolved
 
+        # Fall back to the first tag that is usable as a folder name. The raw
+        # tag list can contain keyword dumps that would become unusable folders
+        # and break path length limits, so skip those (#1119).
         for tag in tags:
-            if isinstance(tag, str) and tag:
-                return tag
+            if is_usable_path_tag(tag):
+                return tag.strip()
         return ""
 
     def get_priority_tag_suggestions(self) -> Dict[str, List[str]]: