v8.4.0

• fix(ci): expect shadow durable-memory mode to fail at decode
• fix(ci): stop pre-analysis from draining mock queues on Windows
• fix(ci): expect Go SDK capabilities v2 and surface LLM root causes
• fix(ci): restore a3s-sandbox registry source in Cargo.lock
• fix(ci): rustfmt drift and clippy --all-features for thin default
• fix(ci): pin a3s-sandbox crates.io source in Cargo.lock
• fix(ci): unblock v8.4.0 release after thin-harness defaults
• docs: first-principles README and v8.4 site for thin harness
• chore: refresh Cargo.lock for --locked release CI
• docs: prettier-format v8.4.0 guide pages for site CI
• release: a3s-code v8.4.0 harness convergence
• feat: runtime agent style + lazy lexical catalog attach
• docs: add Chinese README and language switcher
• docs: add Chinese README and language switcher
• docs: add Chinese README language switcher
• docs: publish v8.3.0 website and feature guides