fix(bench): remove references to deleted Python diffctx modules

Author: nikolay-e

benchmarks/contextbench_diffctx.py

@@ -169,14 +169,11 @@ def run_baseline_bm25(repo_dir: Path, budget: int = 8000) -> dict | None:
 
 
 def _get_diffctx_config() -> dict:
-    from treemapper.diffctx.config.limits import UTILITY as _UTILITY
-    from treemapper.diffctx.filtering import _LOW_RELEVANCE_THRESHOLD, _MAX_CONTEXT_FRAGMENTS_PER_FILE
-
     return {
-        "low_relevance_threshold": _LOW_RELEVANCE_THRESHOLD,
-        "proximity_decay": _UTILITY.proximity_decay,
-        "peripheral_cap": _UTILITY.peripheral_cap,
-        "max_context_frags_per_file": _MAX_CONTEXT_FRAGMENTS_PER_FILE,
+        "low_relevance_threshold": 0.015,
+        "proximity_decay": 0.30,
+        "peripheral_cap": 0.15,
+        "max_context_frags_per_file": 30,
     }
 
 
@@ -452,9 +449,7 @@ def _print_cross_seed_summary(all_seed_results: dict[int, list[dict]]) -> None:
 def main():
     import argparse
 
-    from treemapper.diffctx.filtering import _LOW_RELEVANCE_THRESHOLD
-
-    print(f"diffctx _LOW_RELEVANCE_THRESHOLD = {_LOW_RELEVANCE_THRESHOLD}", file=sys.stderr)
+    print("diffctx backend: Rust (_diffctx)", file=sys.stderr)
 
     parser = argparse.ArgumentParser()
     parser.add_argument("--limit", type=int, default=3)