chore: prepare 0.1.0 for crates.io publish

- Cargo.toml: add documentation and readme fields; expand the exclude
  list so deny.toml, justfile, mise.toml, .github, .jj, fuzz, and any
  cargo-mutants output never ship in the published tarball.
- README: badges, install snippet for both feature shapes, testing
  matrix.
- CHANGELOG.md: keep-a-changelog skeleton with a 0.1.0 entry.
- Revert framing.rs let-chain back to nested if-let so the published
  MSRV holds at the edition-2024 floor (1.85). Behaviour unchanged.

cargo publish --dry-run packages cleanly.

CHANGELOG.md

@@ -0,0 +1,31 @@
+# Changelog
+
+All notable changes to this crate are documented here. The format
+follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and
+this project adheres to [Semantic Versioning](https://semver.org/).
+
+## 0.1.0 — 2026-04-13
+
+Initial release. The DongLoRa wire-protocol types and COBS framing,
+extracted from the firmware so the firmware, `client-rs`, `mux-rs`,
+and `bridge` can share one definition.
+
+### Added
+
+- Wire types: `Command`, `Response`, `RadioConfig`, `Bandwidth`,
+  `ErrorCode`, plus the `MAX_PAYLOAD`, `RADIO_CONFIG_SIZE`,
+  `TX_POWER_MAX`, and `PREAMBLE_DEFAULT` constants. Fixed-width
+  little-endian on the wire — see the firmware repo's `PROTOCOL.md`.
+- `framing` module: streaming `CobsDecoder` plus `cobs_encode_response`,
+  with a `MAX_FRAME` constant sized to fit any valid `Response` after
+  COBS overhead.
+- Cargo features: `defmt` (default, derives `defmt::Format` on public
+  enums) and `std` (off, opt-in for host-side `Debug` niceties).
+- Test surface: 23 proptest properties (~1.13M cases per run), 4
+  cargo-fuzz targets, 16 canonical wire-byte vectors anchored to the
+  spec, 6 mutation-killers. Mutation testing reaches 89/89 viable
+  mutants under both feature configurations (3 provably-equivalent
+  mutants documented and excluded). Miri runs clean on the library
+  and the canonical-vector tests.
+- `forbid(unsafe_code)` at the crate root.
+- GitHub Actions CI (test/clippy/fmt/doc/deny/miri/fuzz/mutants).