feat(logs): retain bounded session output

[msmps]

Summary

• retain a bounded raw-output tail for every live session
• add protocol-gated logs and per-session retention overrides
• read the daemon retention default once from PILOTTY_RETAIN_BYTES
• write exact raw bytes to stdout and retention accounting to stderr
• document the new command and configuration

Compatibility

• existing spawn requests remain compatible with protocol 0
• retention overrides and logs require protocol 1
• current clients probe older daemons and reject logs before transmission

Verification

• cargo test --all
• cargo clippy --all --benches --tests --examples --all-features -- -D warnings
• cargo fmt --all -- --check
• manual isolated-daemon validation with an 8-byte ring confirmed exact retained bytes and truncation accounting