feat(ds-stream): v2.0-2.3 composable codec pipeline
v2.0 — Pipeline Architecture
- Frame, CodecResult, Codec trait, Pipeline builder
- 6 adapters: Passthrough, Dedup, Compress, Pacer, Slicer, Stats
v2.1 — Multi-frame & new codecs
- CodecOutput::Many fan-out, EncryptCodec, FilterCodec
- Codec::reset(), encode_all/decode_all, real SlicerCodec chunking
v2.2 — Observability & reassembly
- PipelineResult (frames+errors+consumed), StageMetric
- ReassemblyCodec, ConditionalCodec, Pipeline presets & metrics
v2.3 — Integrity & rate control
- ChecksumCodec (CRC32), RateLimitCodec (token bucket), TagCodec
- Pipeline::chain(), Pipeline::describe()
13 codec adapters, 474 tests (all green, 0 regressions)
35b39a1cf1