Labels: good first issue, help wanted, area:docs, area:i18n
Difficulty: M (~half a day; requires fluent Japanese)

Context

Shipped docs are English-canonical with Japanese companions (docs/README.md,
"Languages" section). Companions exist for attach-mode, ingestion-contract, and two
example-adapter READMEs — but not for the highest-traffic page for new users,
docs/getting-started.md (~245 lines: install, quickstart, manual steps,
troubleshooting).

What to do

1. Translate docs/getting-started.md into docs/getting-started.ja.md, following the
   established pattern:
   • JA file top banner: > English (canonical): [getting-started.md](./getting-started.md) — synced to this content as of commit <short-sha>. … (see docs/attach-mode.ja.md:3;
     use the short SHA of the public-mirror commit you translated from — maintainers may
     adjust the marker on import).
   • EN file gets the reciprocal link line > 日本語版: … near the top (see
     docs/attach-mode.md:3).
2. Translate faithfully — EN is canonical; do not add, soften, or strengthen any claim.
   Keep all commands, ports, env var names, and paths byte-identical.
3. Update the "Languages" list in docs/README.md to include the new companion.
   While there: the list currently omits the existing
   docs/examples/gemini-adapter/README.ja.md — add it in the same PR.

Acceptance criteria

• Heading structure of getting-started.ja.md mirrors the EN file one-to-one.
• Commands / ports / env names identical to EN; sync marker present.
• docs/README.md languages list is complete (new companion + the missing gemini entry).
• pnpm format green.