Phase 20: Dedicated tag field — chip input, explicit tags array

Tags are now a first-class field rather than being auto-extracted from
the note body. A new TagInput.vue chip component handles tag entry in
both editor views with autocomplete, Enter/comma/backspace UX, and
space-to-hyphen sanitization.

Backend:
- routes/notes.py: create reads tags from JSON; update accepts explicit
  tags (omit = keep existing); append_tag writes to tags array with
  dedup; suggest-tags accepts current_tags filter; remove extract_tags
- routes/tasks.py: same — explicit tags on create/update; remove extract_tags
- services/tag_suggestions.py: current_tags param replaces body extraction
- services/tools.py: create_note tool schema adds tags param; executor passes it
- services/llm.py: system prompt tells LLM to use tags param, not embed #tag in body

Frontend:
- components/TagInput.vue: new chip-based tag input (autocomplete, keyboard UX)
- NoteEditorView.vue / TaskEditorView.vue: tags ref loaded from note.tags;
  TagInput placed between title and body; save/autosave include tags; suggest
  now adds chips; fetchTagSuggestions passes current_tags; dirty tracks tags
- TiptapEditor.vue: remove fetchTags prop and TagSuggestion extension;
  keep TagDecoration for legacy inline #tag highlighting

No DB migration needed — tags column already correct.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/routes/tasks.py

@@ -11,7 +11,6 @@ from fabledassistant.services.notes import (
     list_notes,
     update_note,
 )
-from fabledassistant.utils.tags import extract_tags
 
 tasks_bp = Blueprint("tasks", __name__, url_prefix="/api/tasks")
 
@@ -60,7 +59,7 @@ async def create_task_route():
     uid = get_current_user_id()
     data = await request.get_json()
     body = data.get("body", "") or data.get("description", "")
-    tags = extract_tags(body)
+    tags = data.get("tags", [])
 
     due_date = None
     if data.get("due_date"):
@@ -121,8 +120,8 @@ async def update_task_route(task_id: int):
         else:
             fields["due_date"] = None
 
-    if "body" in fields:
-        fields["tags"] = extract_tags(fields["body"])
+    if "tags" in data:
+        fields["tags"] = data["tags"]
 
     task = await update_note(uid, task_id, **fields)
     if task is None: