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/briefing_tools.py

@@ -1,62 +1,9 @@
-"""
-Curated read-only tool subset for agentic briefings.
+"""Briefing tool subset — delegates to the registry's ``briefing=True`` filter.
 
-The main chat pipeline exposes 40+ tools via ``tools.get_tools_for_user``,
-including mutating tools (``create_task``, ``delete_note``) and
-external-search tools (``search_images``, ``search_web``). Neither is
-appropriate for a scheduled background job that generates briefings —
-briefings are read-only and should not reach out to the internet on the
-user's behalf, and leaving high-noise tools in the list increases the
-chance of spurious calls (e.g. ``search_images`` firing on "what
-meeting?").
-
-This module maintains an explicit allowlist. New tools added to
-``tools.py`` are not automatically exposed to briefings — they must be
-opted in by name here.
+Tools are opted-in to briefings via ``@tool(briefing=True)`` in their
+respective module, so there is no separate allowlist to maintain here.
 """
 
-import logging
+from fabledassistant.services.tools import get_briefing_tools
 
-from fabledassistant.services.tools import get_tools_for_user
-
-logger = logging.getLogger(__name__)
-
-# Explicit allowlist — tools a briefing is permitted to call. Read-only only.
-# Any tool not listed here is invisible to the briefing model.
-BRIEFING_TOOL_NAMES: frozenset[str] = frozenset({
-    # Tasks — what's actionable today, overdue, or high priority
-    "list_tasks",
-    # Calendar — internal event store and CalDAV (if configured)
-    "list_events",
-    "search_events",
-    # Weather — today's forecast for the user's configured locations
-    "get_weather",
-    # News — RSS items filtered by user preferences
-    "get_rss_items",
-    # Projects — context for prioritization and narrative continuity
-    "list_projects",
-    "search_projects",
-    "get_project",
-    # Notes — surface recent captures for "pick up where you left off"
-    "list_notes",
-    "get_note",
-})
-
-
-async def get_briefing_tools(user_id: int) -> list[dict]:
-    """Return the tool schemas a briefing run is permitted to call.
-
-    Builds the user's full tool list (so user-specific gating such as
-    CalDAV availability still applies) and filters it down to the
-    briefing allowlist.
-    """
-    all_tools = await get_tools_for_user(user_id)
-    filtered = [
-        t for t in all_tools
-        if t.get("function", {}).get("name") in BRIEFING_TOOL_NAMES
-    ]
-    logger.debug(
-        "Briefing tools for user %d: %d of %d selected",
-        user_id, len(filtered), len(all_tools),
-    )
-    return filtered
+__all__ = ["get_briefing_tools"]