Deletes ~760 lines of legacy briefing code: format_task, compute_task_hash,
upsert_task_snapshots, _gather_internal, _gather_weekly_review,
_llm_synthesise, and the unified prompt helpers. run_compilation and
run_slot_injection are now agentic-tool-use-loop only.
briefing_scheduler and user_profile migrated from the deleted helper to
services.llm.generate_completion (retry + keep_alive baked in).
routes/briefing.manual_trigger now persists agentic tool-call receipts
via _persist_agentic_messages (previously silently dropped them) and
adds POST /api/briefing/reset-today to wipe today's briefing messages.
BREAKING: briefing_mode setting no longer honored; no legacy fallback.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>