docs(changelog): sealed EncodingId + typed ArrayNode

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: dfa1

CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `Compute.filteredSum` over a dictionary-encoded filter column is ~20× faster (best runs ~30×): the predicate is resolved against the dictionary's value pool once and the raw `u8` codes are scanned directly from their backing segments, instead of decoding every row through the per-element accessor — a fused `SUM(measure) WHERE category = …` over 100M rows drops from ~760 ms to ~38 ms. ([85e251cc](https://github.com/dfa1/vortex-java/commit/85e251cc))
 - `Compute.filteredAggregate` takes the same dictionary code-scan lane (`COUNT(*)` included) — ~22× faster on the same workload (~980 ms → ~46 ms over 100M rows), which the Calcite `WHERE`-filtered aggregate push-down inherits on its boundary chunks. ([145791c7](https://github.com/dfa1/vortex-java/commit/145791c7), [6e6d7dd0](https://github.com/dfa1/vortex-java/commit/6e6d7dd0))
 - A multi-column `AND` filter no longer forfeits the dictionary lane: the dict-encoded leaf drives the code scan and the remaining predicates are evaluated only on its matches — `SUM(…) WHERE category = 7 AND price > 500` over 100M rows drops from ~2.3 s to ~200 ms (~11×). ([12e13501](https://github.com/dfa1/vortex-java/commit/12e13501))
+- `core.model.EncodingId` is now a sealed interface: the spec constants live in the nested `WellKnown` enum (re-exported, so `EncodingId.VORTEX_FOO` call sites compile unchanged) and `Custom` wraps any other wire string, which for the first time lets third-party `EncodingDecoder`/`EncodingEncoder` implementations declare ids outside the spec set. `parse` is total over non-blank ids — an unknown id yields a typed `Custom` instead of an empty `Optional`. ([ea88a91b](https://github.com/dfa1/vortex-java/commit/ea88a91b))
+- `reader.decode.ArrayNode` is a single record carrying the typed `EncodingId`; the `KnownArrayNode`/`UnknownArrayNode` split and the `ArrayNode.of` factory are gone. Decode dispatch, the `allowUnknown` passthrough, and error messages are unchanged. A crafted file with a blank encoding id now fails as `VortexException` instead of escaping as `IllegalArgumentException`. ([21810d7e](https://github.com/dfa1/vortex-java/commit/21810d7e))
 
 ## [0.11.0] — 2026-06-28