Run benchmark tests (--test mode) in CI instead of full benchmarks

Full criterion benchmarks take >30 minutes even with reduced settings.
Changed CI to run `cargo bench -- --test` which:
- Validates benchmarks compile and execute correctly
- Runs each benchmark once without statistical analysis
- Completes in seconds rather than minutes

Also reduced link counts to 100 for faster CI validation.

For actual performance measurements, run locally:
  BENCHMARK_LINK_COUNT=1000 BACKGROUND_LINK_COUNT=3000 cargo bench

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: konard

.github/workflows/rust.yml

@@ -72,8 +72,8 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-cargo-bench-
 
-      - name: Run benchmarks
-        run: cargo bench
+      - name: Run benchmark tests
+        run: cargo bench -- --test
         env:
-          BENCHMARK_LINK_COUNT: 1000
-          BACKGROUND_LINK_COUNT: 3000
+          BENCHMARK_LINK_COUNT: 100
+          BACKGROUND_LINK_COUNT: 100