docs: mark vortex.pco encode as supported

- compatibility.md: pco encode column ✅ with mode list (Classic +
  Consecutive delta + IntMult; FloatMult/FloatQuant deferred)
- TODO.md: pco encode item updated to track only the deferred float modes
- CHANGELOG.md: [Unreleased] section with pco encoder, LeBitWriter,
  and ADR 0009 entries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

CHANGELOG.md

@@ -5,6 +5,18 @@ All notable changes to **vortex-java** are documented here.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- `vortex.pco` encoder (`PcoEncodingEncoder`) — Classic mode + Consecutive delta + IntMult mode (mode=1); 4-way interleaved tANS; histogram + bin-optimization DP; multi-chunk (64K-element chunks); all 8 supported ptypes (I16/U16/I32/U32/F32/I64/U64/F64) ([1bb14ab](https://github.com/dfa1/vortex-java/commit/1bb14ab), [086aa52](https://github.com/dfa1/vortex-java/commit/086aa52), [30579ed](https://github.com/dfa1/vortex-java/commit/30579ed), [7219974](https://github.com/dfa1/vortex-java/commit/7219974), [f856559](https://github.com/dfa1/vortex-java/commit/f856559))
+- `LeBitWriter` — LSB-first bit writer, symmetric to `LeBitReader`; reusable for future bit-oriented encoders ([1bb14ab](https://github.com/dfa1/vortex-java/commit/1bb14ab))
+- ADR 0009 — write API ergonomics (DType factories, `structBuilder`, typed `Chunk` builder, `MemorySegment` zero-copy overload) ([d9c4b99](https://github.com/dfa1/vortex-java/commit/d9c4b99), [a57ea70](https://github.com/dfa1/vortex-java/commit/a57ea70))
+
+### Notes
+
+- Pco encode FloatMult / FloatQuant modes deferred — marginal gain over existing Classic+ALP cascade.
+
 ## [0.6.0] — 2026-06-13
 
 **proto-rewrite** (`protobuf-java` → in-tree MemorySegment-native codec, CLI −14%),

TODO.md

@@ -134,5 +134,5 @@ See [docs/compatibility.md](docs/compatibility.md) for the full encoding support
   compression. Encode the validity bitmap as a Bool child (child[0]) in the `EncodeNode`. Mirrors what Rust does: only
   valid values go into the compressed payload.
 
-- [ ] **`vortex.pco` encode** — E0 gate cleared; see [ADR-0007](docs/adr/0007-pco-encode.md) for phases, risks, and estimates. Start with E1 (`LeBitWriter`).
+- [ ] **`vortex.pco` encode — FloatMult / FloatQuant modes** — Classic + Consecutive delta + IntMult ship; FloatMult/FloatQuant deferred. Marginal gain over existing Classic+ALP cascade; significant complexity (approx pair-GCD, false position root finder, trailing-zero detector).
 

docs/compatibility.md

@@ -66,7 +66,7 @@ resolves only the standalone decoders in `reader`; no encoder class is loaded.
 | `vortex.decimal`            | `DecimalEncodingDecoder`         | `DecimalEncodingEncoder`         | ✅      | ✅      |                                                                       |
 | `vortex.decimal_byte_parts` | `DecimalBytePartsEncodingDecoder`| `DecimalBytePartsEncodingEncoder`| ✅      | ✅      |                                                                       |
 | `vortex.datetimeparts`      | `DateTimePartsEncodingDecoder`   | `DateTimePartsEncodingEncoder`   | ✅      | ✅      |                                                                       |
-| `vortex.pco`                | `PcoEncodingDecoder`             | `PcoEncodingEncoder`             | ✅      | ❌      | Decode: all modes; encode not yet implemented                         |
+| `vortex.pco`                | `PcoEncodingDecoder`             | `PcoEncodingEncoder`             | ✅      | ✅      | Decode: all modes. Encode: Classic + Consecutive delta + IntMult; FloatMult/FloatQuant deferred |
 | `fastlanes.bitpacked`       | `BitpackedEncodingDecoder`       | `BitpackedEncodingEncoder`       | ✅      | ✅      | Unsigned integer PTypes                                               |
 | `fastlanes.delta`           | `DeltaEncodingDecoder`           | `DeltaEncodingEncoder`           | ✅      | ✅      | Integer PTypes                                                        |
 | `fastlanes.for`             | `FrameOfReferenceEncodingDecoder`| `FrameOfReferenceEncodingEncoder`| ✅      | ✅      | Integer PTypes                                                        |