Improve signal quality (Exa news category) and remove mock fallback

Exa harvester:
- EXA_CATEGORY=news (default) restricts to news articles, excluding evergreen
  careers/marketing landing pages that were producing irrelevant signals.
- Event-focused query (acquisition/earnings/launch/leadership), dropped
  hiring/career terms that pulled recruiting pages.
- Domain scoping now OFF by default (broad-web news about the account beats
  first-party careers pages); add EXA_EXCLUDE_DOMAINS and loop --domain-filter.

LLM layer:
- Remove the mock reasoner entirely (no provider => loop refuses to run).
- On HTTP 429, WAIT (LLM_RATELIMIT_WAIT_SECONDS, default 900s; honors
  Retry-After) and retry up to LLM_RATELIMIT_MAX_RETRIES (24) instead of
  degrading to mock output.
- If the LLM is ultimately unavailable for an account, skip it and leave its
  signals unconsumed (retried next run) — never fabricate briefs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sales-agent/src/connectors/exa.py

@@ -84,18 +84,18 @@ def _count_request() -> None:
 
 
 def _build_query(account: dict, domain_scoped: bool) -> str:
+    # Event-focused: target datable business events, NOT evergreen pages. We avoid
+    # generic words like "hiring"/"careers" that pull recruiting landing pages.
     name = account["accountName"]
-    if domain_scoped:
-        # Domain is already restricting results, so keep the query topical/broad.
-        return (
-            f"{name} announcements: funding, acquisition, merger, leadership change, "
-            f"strategy, restructuring, product launch, hiring, earnings, partnership"
-        )
-    # No domain restriction -> anchor harder on the company name to limit drift.
-    return (
-        f'"{name}" company news: funding, acquisition, merger, leadership change, '
-        f"strategy, restructuring, product launch, hiring, earnings, partnership"
+    events = (
+        "acquisition, merger, earnings results, product launch, partnership, "
+        "expansion, restructuring, layoffs, leadership change, executive appointment, "
+        "data center, cloud, modernization, regulatory, strategy"
     )
+    if domain_scoped:
+        return f"{name} news and announcements: {events}"
+    # No domain restriction -> anchor on the exact company name to limit drift.
+    return f'"{name}" news: {events}'
 
 
 def harvest_news(account: dict) -> list[RawSignal] | None:
@@ -117,8 +117,12 @@ def harvest_news(account: dict) -> list[RawSignal] | None:
         "startPublishedDate": start,
         "contents": {"text": {"maxCharacters": 1000}},
     }
+    if config.EXA_CATEGORY:
+        payload["category"] = config.EXA_CATEGORY
     if domain_scoped:
         payload["includeDomains"] = [domain]
+    if config.EXA_EXCLUDE_DOMAINS:
+        payload["excludeDomains"] = config.EXA_EXCLUDE_DOMAINS
     req = urllib.request.Request(
         _ENDPOINT,
         data=json.dumps(payload).encode("utf-8"),
@@ -162,7 +166,8 @@ def harvest_news(account: dict) -> list[RawSignal] | None:
             )
         )
     remaining = usage_status()["monthly_remaining"]
+    cat = config.EXA_CATEGORY or "any"
     scope = f"domain={domain}" if domain_scoped else "broad web"
-    print(f"   [exa] {len(signals)} article(s) for {account['accountName']} ({scope}) "
+    print(f"   [exa] {len(signals)} {cat} article(s) for {account['accountName']} ({scope}) "
           f"(monthly budget left: {remaining}/{config.EXA_MONTHLY_REQUEST_CAP})")
     return signals