fix(asapedgeprocessor): feed CountMinSketch KindBytes so it records frequencies

[zzylol]

What

For family: countminsketch, the fused asap_edge processor recorded nothing: it emitted a CountMinSketch envelope shell every window but never counted any frequencies. This fixes that and adds a regression test that asserts a real count.

Root cause

warm_sketch.go's observe built Value: precompute.FloatValue(val) for every family. But sketches.CMSObserver is the only observer that requires KindBytes (cms.go:263) — it hashes the encoded attribute key to count series cardinality, not the numeric value. So for CMS:

1. ObserveKeyed → CMSObserver.Observe returned "expected KindBytes, got Float" and never called InsertHash.
2. The series was still admitted (empty sketch), so Drain emitted an envelope with data points.
3. The observe error was discarded with _ =.

Net: an envelope was emitted while zero frequencies were recorded — and the existing all_families smoke test (asserts DataPointCount() != 0) stayed green, hiding it.

Fix

• For the CMS family, build the observation value as BytesValue(AttributesKey(labels, nil)) — the full attribute key, matching the standalone countminsketchprocessor shim (shim_helpers.go:58). AggregateBy grouping is applied separately by SeriesKeyFor, so the inserted key stays the full attribute set (nil), preserving query-time parity.
• Stop swallowing the ObserveKeyed error: retain it on the aggregator and log it once. This silent _ = is exactly what hid the bug.
• CountSketch is unaffected — its observer takes KindFloat (countsketch.go:211). Only CMS needed KindBytes.

Test

TestCountMinSketchRecordsFrequency drives 40 CMS observations through the fused observe, reconstructs the emitted CMS from the envelope payload (ApplyDelta), and asserts EstimateCount(key) >= 40. It fails without the fix (CMSObserver: expected KindBytes, got Float) and passes with it. go build/vet/test ./... all green.

Based on top of the reorg (#448), so the fix lives in warm_sketch.go.

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