refactor(hllprocessor): thin shim delegating to asap-precompute-go (Phase 2 step 2.7)

[zzylol]

Summary

• HLL processor refactored into a thin shim that delegates the windowing, snapshot caching, and delta encoding state machine to the host-neutral asap-precompute-go runtime (ADR-0002, Phase 2 step 2.7).
• sketch_wrapper.go implements precompute.Sketch + precompute.CardinalitySketch over sketchlib-go HLL; EstimateCardinality() is the new typed entry point pinned in PR feat(asap-precompute-go): SketchEnvelope MetricName/Count/Temporality + Sketch trait split #224.
• Structurally mirrors PR refactor(kllprocessor): thin shim delegating to asap-precompute-go (Phase 2 step 2.6) #226 (KLL): per-input-metric Precompute map keyed by metric name, OmitResourceAttrs=true + EmitWindowStats=false parity flags, public ProcessBatch / ProcessMetrics / FlushWindow test API per ADR-0002 §"Test API contract".

LoC delta

processor.go shrinks from 786 LoC → 264 LoC (state machine moves to runtime). New files: sketch_wrapper.go (216), encode.go (235), selfmonitor.go (63). Total production LoC: 995 across 6 files.

Parity result

TestParity_HLL passes byte-identical (3 envelopes match). Full parity suite green:

=== RUN   TestParity_HLL
    parity_test.go:105: parity OK: 3 envelopes matched byte-for-byte
--- PASS: TestParity_HLL (0.47s)

Notes

• HLL output emits AggregationTemporalityCumulative (not Delta like KLL) — matches legacy.
• Default output metric name is <input>_hll_cardinality; MetricSuffix overrides as before.
• FlushWindow uses a monotonically-advancing pseudo-tick timestamp so repeated forced rotations don't get stuck on the same already-advanced bucket.
• Cardinality reconstruction for delta-encoded outbound dps is done in the shim's encode layer (per-series snapshot map keyed by (metric, series-attrs)) since the runtime drops the live sketch handle after Tick.

Test plan

• go test ./... in opentelemetry-collector-contrib-patch/processor/hllprocessor (8 tests, including delta_transmission_test.go and integration_test.go)
• go test -race ./... clean
• go vet ./... clean
• go test -v -run TestParity_HLL ./integration/parity/... byte-identical
• Full parity suite (go test ./integration/parity/...) green

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