docs: explain per-command environment selection

[jg-noncelogic]

Summary

• document --env as a per-command environment selector in the Quick start
• show the requested run and ls examples
• keep all four translated READMEs structurally aligned with English

Closes #148.

Verification

• scripts/check-readme-i18n
• python3 -B -m unittest scripts.tests.test_readme_i18n -v (13 passed)
• git diff --check
• confirmed in crates/cli/src/main.rs that --env is global and overrides the configured default for the command

The full Rust suite was not run because Cargo is unavailable in this environment. The change is documentation only.

Authored with AI assistance and reviewed against the repository's contribution guidance.

[github-actions]

Thanks for your first pull request to Sotto, and welcome.

Two things that trip up newcomers:

• Every commit needs a Signed-off-by line under the Developer Certificate of Origin - PRs with unsigned commits cannot be merged. Sign off with git commit -s; if your branch already has unsigned commits, run git rebase --signoff main and push again.
• Please run cargo fmt --all --check and cargo clippy --workspace --all-targets -- -D warnings before pushing, and add tests for new behaviour (cargo test --workspace runs the suite).

The full guide is in CONTRIBUTING.md - a maintainer will review shortly.

[Maxerns]

Thanks @jg-noncelogic I confirmed the per command semantics against the --env definition in main.rs. Translations across all four READMEs appreciated too. Approving ci now and ill merge when its green