The 15 rolling micro-compaction methods (cursor resolution, exchange
serialization, one-exchange summarization, defrag, splice, DB sync, telemetry)
move verbatim into MicroCompactionMixin, mixed into ContextCompressor
(MRO: ContextCompressor -> MicroCompactionMixin -> ContextEngine). Origin
constants and call_llm are imported lazily so tests patching
agent.context_compressor.X still apply; logger name parity is kept.