fix(MAT-174): Stricter LLM filter prompt — exclude when in doubt

Require ALL criteria to clearly match. Exclude general articles,
category pages, unconfirmed locations. When in doubt, exclude.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cron/brave_search.py

@@ -15,10 +15,15 @@ LITELLM_URL = os.environ.get("LITELLM_BASE_URL", "")
 LITELLM_KEY = os.environ.get("LITELLM_API_KEY", "")
 FILTER_MODEL = os.environ.get("BASE_MODEL", "claude-haiku")
 
-FILTER_SYSTEM_PROMPT = """You are a search result filter. Given a list of search results and filtering criteria, evaluate each result and return ONLY the ones that match the criteria.
+FILTER_SYSTEM_PROMPT = """You are a strict search result filter. Given search results and filtering criteria, evaluate each result's title and description against ALL criteria. A result must clearly match EVERY criterion to be included. When in doubt, EXCLUDE.
 
-Return a JSON array of indices (0-based) of results that match. If none match, return an empty array [].
-Only return the JSON array, nothing else."""
+Rules:
+- If a result is a general article, category page, or ad rather than a specific listing, EXCLUDE it.
+- If the location/region cannot be confirmed from the title or description, EXCLUDE it.
+- If any single criterion is not met or unclear, EXCLUDE the result.
+
+Return ONLY a JSON array of matching indices (0-based). If none match, return [].
+No explanation, just the array."""
 
 
 async def _llm_filter(results: list[dict], criteria: str) -> list[dict]: