fix: harden decoupled L3 contracts

[ZhiXiao-Lin]

Summary

Follow-up to #4, which merged while review validation was running.

• preserve incomplete ToolExec evidence as an L1 escalation when the daemon worker queue is full, instead of resolving it through fail-open
• add an end-to-end overload regression test and clarify the daemon audit-only boundary versus durable external L3 dispatch
• generate Promise for the asynchronous TypeScript API instead of Promise
• omit escalationCause once L2 has produced a completed allow or block decision
• add TypeScript SDK build and test coverage to pull-request CI

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace --all-targets: 67 unit + 13 integration passed
• cargo test --doc
• RUSTDOCFLAGS=-D warnings cargo doc --workspace --no-deps
• cargo package --allow-dirty
• cargo clippy --manifest-path sdk/typescript/Cargo.toml --all-targets -- -D warnings
• npm ci
• npm run build
• npm test: 12 passed
• npm pack --dry-run --json
• overload regression repeated five times
• git diff --check