Revert root directory pollution from PR Rapsssito#220

Removed non-bounty files that polluted root directory:
- bench-ab.js (benchmark script, not requested)
- rope-viz.js (visualization helper, should be inline or test util)
- README.md formatting changes (reverted to 81ad117)

Kept core bounty deliverables:
- src/FrameCodec*.js optimizations (zero-copy varint, circular buffer)
- src/Socket.js allocation hotspot fixes
- test-tug-of-war.js (consolidated DRY test suite)
- test-codec-variance-tug-of-war.js (warm JIT variance testing)
- test-libp2p-handshake.js, test-tcp.js (pre-existing)

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