issues, chat FPS; optimisations

.scratch/distributed-inference-performance/issues/07-prefill-backpressure.md

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+Status: ready-for-agent
+
+# 07 — Bounded prefill chunk backpressure
+
+## What to build
+
+Make large prefill transfer bounded across every Activation Seam. Chunk prompt
+activations, limit in-flight chunks, and propagate downstream congestion so a
+slow Shard node cannot cause the head or relay bridge to buffer the entire
+context in memory. Keep decode-step traffic sequential and low-latency.
+
+## Acceptance criteria
+
+- [ ] Configurable prefill chunk size and in-flight limit exist with safe
+  defaults.
+- [ ] Peak per-hop buffered bytes are bounded by the configured limits.
+- [ ] A slow downstream stub applies backpressure and does not lose or reorder
+  chunks within a Route Session.
+- [ ] Cancellation and route failure release queued chunks and local buffers.
+- [ ] Tests cover small prompts, multi-chunk prompts, slow consumers, retry/fail
+  closeout, and legacy single-chunk peers.
+
+## Blocked by
+
+- 01 — Baseline and profiling harness.
+- 04 — Activation Seam telemetry and bounded progress reporting.
+