refactor(tools): decorator-based tool registry replaces monolithic tools.py

Split 2566-line tools.py into a tools/ package with @tool decorator
registration. Each tool's schema, metadata, and implementation live
together. Briefing eligibility is now a briefing=True flag instead of
a separate frozenset allowlist. Conditional inclusion (CalDAV, SearXNG)
uses requires= metadata. Public API (get_tools_for_user, execute_tool)
unchanged.

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

src/fabledassistant/services/tools/_helpers.py

@@ -0,0 +1,77 @@
+"""Shared utilities used across tool modules."""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+import re
+from datetime import date, datetime
+from difflib import SequenceMatcher
+
+logger = logging.getLogger(__name__)
+
+_PUNCT_RE = re.compile(r"[^\w\s]")
+
+
+def schedule_embedding(note_id: int, user_id: int, title: str, body: str) -> None:
+    """Fire-and-forget: update the embedding for a note after it's created/modified."""
+    from fabledassistant.services.embeddings import upsert_note_embedding
+
+    text = f"{title}\n{body}".strip() if body else (title or "")
+    if text:
+        asyncio.create_task(upsert_note_embedding(note_id, user_id, text))
+
+
+async def resolve_project(user_id: int, project_name: str):
+    """Exact-then-fuzzy project lookup. Returns the Project or None.
+
+    Resolution order:
+    1. Exact title match (case-insensitive via DB)
+    2. project_name is a substring of an existing title
+    3. Existing title is a substring of project_name
+    4. SequenceMatcher ratio >= 0.55
+    """
+    from fabledassistant.services.projects import get_project_by_title, list_projects
+
+    proj = await get_project_by_title(user_id, project_name)
+    if proj is not None:
+        return proj
+    needle = project_name.lower().strip()
+    all_p = await list_projects(user_id)
+    for p in all_p:
+        haystack = p.title.lower().strip()
+        if needle in haystack or haystack in needle:
+            return p
+    best, best_r = None, 0.0
+    for p in all_p:
+        r = SequenceMatcher(None, needle, p.title.lower().strip()).ratio()
+        if r >= 0.55 and r > best_r:
+            best, best_r = p, r
+    return best
+
+
+def parse_due_date(value: str | None) -> date | None:
+    """Parse a due date string, returning None on failure."""
+    if not value:
+        return None
+    try:
+        return datetime.strptime(value, "%Y-%m-%d").date()
+    except (ValueError, TypeError):
+        logger.warning("Invalid due_date format: %s", value)
+        return None
+
+
+def fuzzy_title_match(title: str, candidates, threshold: float = 0.82):
+    """Return (best_match, ratio) if any candidate's title is similar enough.
+
+    Uses SequenceMatcher ratio. Threshold 0.82 catches near-duplicates like
+    "Game Premise" / "Game Premise Notes" while leaving clearly different
+    titles alone. Returns (None, 0.0) when no candidate meets the threshold.
+    """
+    needle = title.lower().strip()
+    best, best_r = None, 0.0
+    for c in candidates:
+        r = SequenceMatcher(None, needle, c.title.lower().strip()).ratio()
+        if r >= threshold and r > best_r:
+            best, best_r = c, r
+    return best, best_r