[proposal] Add a Persian README translation #711

Short description

Add a complete Persian translation of the current README.

What problem does this solve?

Persian-speaking users do not currently have a localized README. The repository already maintains README translations in docs/i18n/, so adding Persian would make the onboarding, setup, feature, and configuration guidance accessible to them without changing product behavior.

Proposed solution

Add docs/i18n/README.fa.md as a complete, manually written translation of the current root README.md. Preserve command names, code blocks, identifiers, and external links, and add a فارسی link in the language switcher at the top of README.md. Keep the English README as the canonical source.

Alternatives considered

Machine translation could reduce effort but risks errors in technical and configuration guidance. Waiting for a future community contribution would leave Persian-speaking users without a localized guide.

Area

Not sure

Additional context

This is a documentation-only localization proposal. It changes no runtime behavior and touches no harness-facing code. The proposed files are docs/i18n/README.fa.md and the language switcher in README.md.