Adds README.es.md, docs/README.es.md, docs/USER-GUIDE.es.md, and
docs/CLI-REFERENCE.es.md mirroring the English client-facing set.
Each English doc gains a one-line language-switch banner pointing at
its Spanish counterpart; the docs index advertises both language sets
in the buyer-facing section. Internal docs (TECHNICAL, DECISIONS,
REQUIREMENTS, BUSINESS, RECOVERY) stay English-only by design — they
don't ship with the product.
The CLI itself emits English only, so CLI-REFERENCE.es.md notes that
flags and values are language-invariant while translating the prose.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
