docs: decide interactive streaming exec boundary

[ZhiXiao-Lin]

Summary

• accept ADR 0003 and keep Runtime v0.2 exec bounded, buffered, unary, and non-interactive
• require a distinct versioned capability plus terminal ownership, backpressure, ordering, cancellation, reconnect, and cleanup semantics before any future interactive protocol
• align the README, implementation plan, and deep-test release oracle with the decision
• prohibit Cloud from presenting direct node access or unary/log emulation as Runtime-compatible streaming exec

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --locked -- -D warnings
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps --locked
• focused deadline test passed after isolating a macOS Unix-socket path-length limitation
• git diff --check
• repository CI remains authoritative for the full locked Linux stable/MSRV test matrix

Progresses #1

[ZhiXiao-Lin]

Merged the typed log-discontinuity change from #3 and resolved the README overlap by retaining both contracts: permanent log gaps are typed, while exec remains bounded, buffered, unary, and non-interactive. Revalidation passed on Rust 1.85: formatting, strict workspace Clippy, the complete locked all-target test suite (including process/crash races and the 10,000+ receipt case), rustdoc with warnings denied, and diff checks.