[ctreffs]

Adds the first committed benchmark report and links it from the README and the DocC Benchmarks article.

• Documentation/Benchmarks/BenchmarkReport.html and BenchmarkReport.manifest.json: 1.4.3 (c85607bf) vs main labelled 2.0.0 (088e9173), baseline 1.4.3
• Full selection (BENCHMARK_FILTER='.*'), 10 replicates, seed 2236095238, 1,383 benchmarks per round, Swift 6.4 (Xcode toolchain) for both refs
• No toolchain, host or benchmark-set warnings; 0 of 1,383 cells show drift across rounds
• README links the latest report (benchmarks/, version-agnostic); Benchmarks/README.md and Benchmarks.md (DocC) also link benchmarks/2.0.0/. Both URLs go live when the 2.0.0 tag publishes the report
• make check-release-report RELEASE_VERSION=2.0.0 and make docs-check-links pass on this branch

Headline (wall clock, 2.0.0 vs 1.4.3): faster on every workload at larger entity counts: iteration 37–89×, system update 24–71×, component add / remove-add 3–7×, entity create 2–6×, lookup 1.4–3.4×. Only entity.create.empty at 1–4 entities is slower (+12–22%).

After merge: make check-release-report RELEASE_VERSION=2.0.0 RELEASE_TO=<merge-commit>, then tag 2.0.0. Keep main frozen until then.