fix(test): add 3.9.0 fnDeps to known regressions in benchmark guard

The fnDeps query latency ~3x regression in 3.9.0 vs 3.7.0 is a
pre-existing main issue caused by openRepo engine routing, not by
this PR. Add to KNOWN_REGRESSIONS to unblock CI while fix is
tracked in PR #869/#870.

Author: carlos-alm

tests/benchmarks/regression-guard.test.ts

@@ -65,8 +65,15 @@ const SKIP_VERSIONS = new Set(['3.8.0']);
  * - 3.9.0:1-file rebuild — native incremental path re-runs graph-wide phases
  *   (structureMs, AST, CFG, dataflow) on single-file rebuilds. Documented in
  *   BUILD-BENCHMARKS.md Notes section with phase-level breakdown.
+ * - 3.9.0:fnDeps depth {1,3,5} — fnDeps query latency ~3x due to openRepo
+ *   engine routing bug causing double-init. Fix tracked in PR #869/#870.
  */
-const KNOWN_REGRESSIONS = new Set(['3.9.0:1-file rebuild']);
+const KNOWN_REGRESSIONS = new Set([
+  '3.9.0:1-file rebuild',
+  '3.9.0:fnDeps depth 1',
+  '3.9.0:fnDeps depth 3',
+  '3.9.0:fnDeps depth 5',
+]);
 
 /**
  * Maximum minor-version gap allowed for comparison. When the nearest