[korexil]

The deeper docs were Chinese only, so English readers who found the README had nothing to follow and English searches had nothing to match.

• docs/pitfalls.en.md, docs/how-it-works.en.md, docs/benchmarks.en.md, translated faithfully: numbers, item numbers, tables, commands and error messages unchanged; qualifiers (estimated, not profiled, one machine, n runs) kept. Pitfall openings are phrased as the symptom people would search for. #29 also gives the English Windows error text; the quoted prompts in Harden the C bridge and the hand-off; add tests and CI #1 and README: demo video #6 note that they are translations.
• The Chinese originals get a language switch line; README.en.md links to the English versions.
• Internal links and anchors checked against GitHub's heading rules.