[Lethe10137]

Adds a byte trigger to the Loss Cell / Loss Replay Cell: after trigger_bytes bytes have passed through the cell's ingress (Input) or egress (Output), the cell drops the next drop_count packets regardless of the configured loss pattern/trace, then returns to normal. It triggers once until the cell is reset. Packet size is counted as L2 length.

• rattan-core/src/cells/loss.rs, config/loss.rs: trigger state and config.
• config.example.toml: documented with an example.

Stack (merge in order, rebase-merge; review the diff against the base branch). This is 1/5:

1. 👉 feat(loss): byte trigger for loss cells #217 feat(loss): byte trigger for loss cells
2. feat: first-payload start, ms granularity timestamp alignment, and drift log #218 feat: first-payload start, mahimahi-like delay, and drift log
3. perf(veth): update tokio and reduce ingress overhead #219 perf(veth): update tokio and reduce veth ingress overhead
4. fix(env): set up netns persist dir once per process #220 fix(env): set up the netns persist directory once per process
5. refactor(env): make Env generic and move I/O drivers into rattan-env #221 refactor(env): make Env generic and move I/O drivers into rattan-env

🤖 Generated with Claude Code

[BobAnkh]

LGTM