Ship anonymized benchmark trace w600_r0.0015_st30 + provenance

Whitelist the sampled replay trace (1214 reqs / 274 sessions / ~600 s) past
the traces/ ignore so the repo is runnable without dash0 access. Metadata
only (token counts, opaque KV-block hashes, timing, session structure) — no
prompts/outputs/PII. traces/README documents schema, provenance (sampled
from the internal GLM-5.1 production trace via scripts/sample_trace.py), and
the regeneration command.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

traces/README.md

@@ -0,0 +1,45 @@
+# Benchmark trace
+
+## `w600_r0.0015_st30.jsonl`
+
+The primary replay trace for the routing / connector experiments
+(1214 requests, 274 sessions, ~600 s span). One JSON object per request:
+
+```json
+{"chat_id": 1237198, "parent_chat_id": -1, "timestamp": 0.0,
+ "input_length": 8228, "output_length": 21, "type": "coder", "turn": 1,
+ "hash_ids": [12292995, ...], "session_id": "1237198"}
+```
+
+| field | meaning |
+|---|---|
+| `input_length` / `output_length` | token **counts** only |
+| `hash_ids` | opaque integer KV-block hashes — shared ids ⇒ shared prefix (drives prefix-cache reuse in replay) |
+| `timestamp` | arrival offset (s) from trace start |
+| `turn` / `parent_chat_id` / `session_id` | multi-turn session structure |
+
+**No cleartext.** There are no prompts, no model outputs, and no PII — only
+token counts, opaque block hashes, timing, and session structure. The replayer
+synthesizes dummy token sequences consistent with `hash_ids` so prefix-cache
+hit rates match the original workload.
+
+### Provenance
+Sampled from the internal Alibaba GLM-5.1-formatted production trace
+(`~/ali-trace/trace-glm5.1-formatted/051315-051317.jsonl` on dash0, ~2.1 M
+requests, 2 h) — not redistributable; only this anonymized sample is shipped.
+The filename encodes the sampling params: `w`=window-seconds, `r`=sample-ratio,
+`st`=max-single-turn-ratio.
+
+Regenerate (requires the dash0 source):
+```bash
+python scripts/sample_trace.py \
+    --input ~/ali-trace/trace-glm5.1-formatted/051315-051317.jsonl \
+    --output traces/w600_r0.0015_st30.jsonl \
+    --window-seconds 600 --sample-ratio 0.0015 --max-single-turn-ratio 0.30 --seed 42
+```
+
+### Replay
+```bash
+python -m replayer --trace traces/w600_r0.0015_st30.jsonl ...
+```
+See `replayer/` and `scripts/cache_aware_proxy.py`.