Status: ready-for-agent

# 04 — Activation Seam telemetry and bounded progress reporting

## What to build

Expose structured timing and byte counters for each Activation Seam while
keeping per-token progress overhead bounded. Report route/session, phase,
hop/node, queue wait, model time, encode/decode time, compression time, wire
bytes, response bytes, and connection reuse. Aggregate high-cardinality events
instead of flushing a log line for every token.

## Acceptance criteria

- [ ] Generation Telemetry includes prefill/decode seam latency and rolling
  tokens/sec without changing token output or cache behavior.
- [ ] Every request can be correlated by stable Route Session plus unique
  activation request id.
- [ ] Counters are sampled or aggregated so telemetry work is bounded and does
  not perform network I/O in the model hot loop.
- [ ] Logs summarize decode progress by session and retain actionable failure
  context.
- [ ] Tests verify counters, aggregation cadence, and cleanup at session close.

## Blocked by

- 01 — Baseline and profiling harness.