refactor(autocomplete): remove old CSV fallback, use TagFTSIndex exclusively

Remove all autocomplete.txt parsing logic and fallback code, simplifying
the service to use only TagFTSIndex for Danbooru/e621 tag search
with category filtering.

- Remove WordEntry dataclass and _words_cache, _file_path attributes
- Remove _determine_file_path(), get_file_path(), load_words(), save_words(),
  get_content(), _parse_csv_content() methods
- Simplify search_words() to only use TagFTSIndex, always returning
  enriched results with {tag_name, category, post_count}
- Remove GET/POST /api/lm/custom-words endpoints (unused)
- Keep GET /api/lm/custom-words/search for frontend autocomplete
- Rewrite tests to focus on TagFTSIndex integration

This reduces code by 446 lines and removes untested pysssss plugin
integration. Feature is unreleased so no backward compatibility needed.

py/routes/handlers/misc_handlers.py

@@ -1202,34 +1202,12 @@ class FileSystemHandler:
 
 
 class CustomWordsHandler:
-    """Handler for custom autocomplete words."""
+    """Handler for autocomplete via TagFTSIndex."""
 
     def __init__(self) -> None:
         from ...services.custom_words_service import get_custom_words_service
         self._service = get_custom_words_service()
 
-    async def get_custom_words(self, request: web.Request) -> web.Response:
-        """Get the content of the custom words file."""
-        try:
-            content = self._service.get_content()
-            return web.Response(text=content, content_type="text/plain")
-        except Exception as exc:
-            logger.error("Error getting custom words: %s", exc, exc_info=True)
-            return web.json_response({"error": str(exc)}, status=500)
-
-    async def update_custom_words(self, request: web.Request) -> web.Response:
-        """Update the custom words file content."""
-        try:
-            content = await request.text()
-            success = self._service.save_words(content)
-            if success:
-                return web.Response(status=200)
-            else:
-                return web.json_response({"error": "Failed to save custom words"}, status=500)
-        except Exception as exc:
-            logger.error("Error updating custom words: %s", exc, exc_info=True)
-            return web.json_response({"error": str(exc)}, status=500)
-
     async def search_custom_words(self, request: web.Request) -> web.Response:
         """Search custom words with autocomplete.
 
@@ -1563,8 +1541,6 @@ class MiscHandlerSet:
             "get_model_versions_status": self.model_library.get_model_versions_status,
             "open_file_location": self.filesystem.open_file_location,
             "open_settings_location": self.filesystem.open_settings_location,
-            "get_custom_words": self.custom_words.get_custom_words,
-            "update_custom_words": self.custom_words.update_custom_words,
             "search_custom_words": self.custom_words.search_custom_words,
         }
 

py/routes/misc_route_registrar.py

@@ -42,8 +42,6 @@ MISC_ROUTE_DEFINITIONS: tuple[RouteDefinition, ...] = (
     RouteDefinition("GET", "/api/lm/metadata-archive-status", "get_metadata_archive_status"),
     RouteDefinition("GET", "/api/lm/model-versions-status", "get_model_versions_status"),
     RouteDefinition("POST", "/api/lm/settings/open-location", "open_settings_location"),
-    RouteDefinition("GET", "/api/lm/custom-words", "get_custom_words"),
-    RouteDefinition("POST", "/api/lm/custom-words", "update_custom_words"),
     RouteDefinition("GET", "/api/lm/custom-words/search", "search_custom_words"),
 )