chore: bump version to 0.3.0, add CHANGELOG

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,49 @@
+# Changelog
+
+## 0.3.0 — 2026-03-31
+
+### Performance
+
+- **Encode nonzero/mixed: ~2x faster** — uses const `copy_from_slice` (memcpy at
+  runtime) via Rust 1.93's stabilization of const slice methods. Sub-slice scan
+  pattern helps LLVM eliminate bounds checks.
+- **Encode zeros: ~50% faster** — fast path skips scan loop overhead for leading
+  zero bytes.
+- **Decode zeros: ~4x faster** — batch consecutive `0x01` codes and fill zeros
+  via `fill(0)` (memset) instead of per-byte iteration.
+- Encode now wins or ties corncobs on nonzero/mixed workloads.
+- Decode zeros now leads all competitors by 3x.
+
+### Added
+
+- `legacy-msrv` feature flag — enables compilation on Rust 1.83+ (e.g. Xtensa
+  toolchain) by replacing const `copy_from_slice` with a manual byte loop.
+  All other optimizations (sub-slice scan, zero fast path, decode batch fill)
+  work without this feature on any supported Rust version.
+
+### Changed
+
+- **MSRV bumped from 1.83 to 1.93** — required for const `copy_from_slice`.
+  Use the `legacy-msrv` feature for older toolchains.
+- Dev-dependencies updated: `cobs` 0.3 to 0.5, `criterion` 0.5 to 0.8,
+  `rand` 0.8 to 0.10.
+
+## 0.2.0 — 2026-03-30
+
+### Added
+
+- `const fn` encode — encode data at compile time with zero runtime cost.
+- Comprehensive documentation with 7 usage examples (basic, buffer sizing,
+  framing, stream parsing, compile-time encoding, error handling).
+- Initial encode/decode throughput optimizations.
+
+### Changed
+
+- MSRV set to 1.83.
+
+## 0.1.0 — 2026-03-29
+
+- Initial release.
+- `no_std`, zero-alloc, `unsafe`-free COBS encoder and decoder.
+- 106 tests: canonical vectors, property-based (proptest), fuzz targets,
+  cross-crate interop with `corncobs` and `cobs`.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ucobs"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 rust-version = "1.93"
 license = "MIT"