Add word-overlap gate to _fuzzy_keyword_match to avoid unnecessary LLM calls

LLM plural check was firing for every non-exact keyword pair (e.g. "insert molding"
vs "cement plant lubrication"), causing timeouts and wasted API calls. Now requires
keywords to share all but one word before escalating to the LLM.

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

cheddahbot/tools/linkbuilding.py

@@ -285,6 +285,15 @@ def _fuzzy_keyword_match(a: str, b: str, llm_check: Callable[[str, str], bool] |
         return True
     if llm_check is None:
         return False
+
+    # Only call LLM when keywords share most words (possible plural difference).
+    words_a = set(a.split())
+    words_b = set(b.split())
+    shared = words_a & words_b
+    total = max(len(words_a), len(words_b))
+    if total > 1 and len(shared) < total - 1:
+        return False
+
     return llm_check(a, b)