test: add Kibana Knip conformance fuzzing

[longlho]

Summary

• add a Kibana/Knip conformance harness that copies the Bazel-fetched Kibana fixture, injects synthetic unused TS files, disables Knip framework plugins, and compares the core TS graph
• document Codescythe's intentional difference from Knip: Codescythe reports every unreachable file in a dead subgraph, while Knip may report only the dead root
• add //benchmarks:kibana_conformance_test as a functional_test Bazel target and split GitHub Actions into normal and functional Bazel test lanes
• refresh the benchmark docs with current Kibana numbers

Test Plan

• node --experimental-transform-types benchmarks/run.ts --fixture kibana --samples 3 --warmups 1 --skip-build
• node --experimental-transform-types benchmarks/kibana_conformance.ts --skip-build --fuzz-files 16
• bazel test //benchmarks:kibana_conformance_test
• bazel test //... --build_tests_only --test_tag_filters=functional_test
• bazel test //... --build_tests_only --test_tag_filters=-functional_test
• node --experimental-transform-types benchmarks/run.ts --help
• node --experimental-transform-types benchmarks/kibana_conformance.ts --help
• git diff --check