feat(streaming): enforce typed completion queues
Replace the flat deferred list, priority scan, unload bypass, and count-only execution cap with exact destination/control/unload/Near/Far FIFOs behind one typed frame meter. Price worker results before adoption, retain exact retry identity, reject stale generations without payload retention, and publish queue pressure through lifecycle diagnostics.
Tests: dotnet build AcDream.slnx -c Release --no-restore; dotnet test AcDream.slnx -c Release --no-restore (8138 passed, 5 skipped)
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