feat: AggID = ASAPQuery-backend PolicyFingerprint, not fnv64(metric name)

[zzylol]

Summary

• Adds PolicyFingerprint (byte-for-byte port of policy_fingerprint.rs's PolicyFingerprint::from_config) plus AggregationIdentity/AggregationRouter SDK-side routing types.
• Wires warm_sketch.go's aggID() to compute the same content-addressed xxh64 hash the backend independently derives from its own AggregationConfig, replacing the old fnv64(metric) computation. AggID used to silently desync between edge and backend for the same policy whenever anything besides the metric name (window, grouping labels, spatial filter, sketch params) differed — CDM and the sketch-DB's materialized-view identity are meant to be one system.
• Adds MetricFamily.SpatialFilter so the edge can include the same normalized spatial predicate the backend hashes.

Context

Split out of #518, whose base (split/pr2-gos) predates the 6-family GOS redesign and the Discipline B split merged into main since. This PR is built fresh against current main. The identity fix itself is sourced from feat/gos-unified-monitoring, where it's already wired end-to-end and byte-identical for the SDK pieces — #518's own branch defines these types but never actually calls them.

First of a 5-PR split (PR-A here; PR-B SDK sampling types, PR-C OTLP wire transport, PR-D collector-side decode, PR-E Rust mirror already open as #537) extracting #518's remaining unmerged scope. #518 will be closed once all land.

Test plan

• go build ./... && go vet ./... && go test ./... in asap-precompute-go — pass
• go vet ./... && go test ./... in the processor (via restore_all.sh) — pass, including updated TestControlPlaneAppliesConfig/TestControlPlanePollLoop (now compute AggID via aggID(...) instead of the retired fnv64)

🤖 Generated with Claude Code