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/services/tools.py

@@ -81,6 +81,11 @@ _CORE_TOOLS = [
                         "type": "string",
                         "description": "The note content in markdown",
                     },
+                    "tags": {
+                        "type": "array",
+                        "items": {"type": "string"},
+                        "description": "Tags for the note (without # prefix, hyphens for multi-word: [\"science-fiction\", \"story/idea\"]). Do NOT embed #tags in the note body.",
+                    },
                 },
                 "required": ["title"],
             },
@@ -710,10 +715,12 @@ async def execute_tool(user_id: int, tool_name: str, arguments: dict) -> dict:
         elif tool_name == "create_note":
             note_title = arguments.get("title", "Untitled Note")
             note_body = arguments.get("body", "")
+            note_tags = arguments.get("tags", [])
             note = await create_note(
                 user_id=user_id,
                 title=note_title,
                 body=note_body,
+                tags=note_tags,
             )
             suggested = await suggest_tags(user_id, note_title, note_body)
             _schedule_embedding(note.id, user_id, note_title, note_body)