prep docs and service updates

docs/benchmarks/signals/bench-sig-26-002-prep.md

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+# Policy Eval with Reachability Cache Prep — PREP-BENCH-SIG-26-002-BLOCKED-ON-26-001-OUTPU
+
+Status: Draft (2025-11-20)
+Owners: Bench Guild · Policy Guild
+Scope: Capture prep for measuring policy evaluation overhead with reachability cache hot/cold, dependent on 26-001 outputs.
+
+## Dependencies
+- Bench outputs from 26-001 (reachability scoring harness) providing cached datasets.
+- Policy overlay schema (30-001) for status fields.
+
+## Proposed benchmarks
+- Scenarios: cold cache, warm cache, mixed workload (70/30), parallel workers.
+- Metrics: added latency per evaluation (p50/p95), cache hit ratio, CPU, memory.
+- Determinism: fixed seed; deterministic request order; stable JSON output ordering.
+
+## Acceptance
+- Reference to reachability dataset hash from 26-001 once available.
+- Config/sample command drafted for `src/Bench/StellaOps.Bench.Policy` (or shared).
+
+## Handoff
+Use this prep doc to satisfy PREP-BENCH-SIG-26-002-BLOCKED-ON-26-001-OUTPU. Update with dataset hash and schema references after 26-001 is done, then move to DONE and unblock BENCH-SIG-26-002.