docs(mocking): translate the history document to English

Everything pushed to GitHub must be in English. The spec 013 history document was
written in French during the design discussions, which failed the CI spell-checking
validation (333 unknown words). spec.md, architecture.md and the reference doc were
already clean.

- history.md fully translated to English, keeping every SHA, type name, file path and
  decision id unchanged.
- implementation.md: replaced three coined words the dictionary rejects (bikesheddable,
  Authorable, mockability) with plain English equivalents.

Verified with the exact CI commands: cspell over 236 markdown files reports 0 issue, and
markdownlint reports no violation.

Author: dr1rrb