docs: document Rust local runtime rollout

[pineapple880066]

Summary

• document the opt-in Docker Compose overlay for the Rust local sandbox runtime
• explain deterministic canary assignment, bounded preflight fallback, and sticky runtime ownership
• document the safe rollback and resource-drain procedure
• update the English, Chinese, and Japanese environment references together

Depends on langgenius/dify#41070.

Validation

• python3 tools/check-links.py --internal
• python3 tools/translate/derive-termbase.py --check
• mintlify validate
• git diff --check