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.

README.md

@@ -1,25 +1,57 @@
 # donglora-protocol
 
-Wire protocol types and COBS framing for DongLoRa, shared between firmware
-and host crates (`client-rs`, `mux-rs`, `bridge`).
+[![CI](https://github.com/donglora/protocol/actions/workflows/ci.yml/badge.svg)](https://github.com/donglora/protocol/actions/workflows/ci.yml)
+[![Crates.io](https://img.shields.io/crates/v/donglora-protocol.svg)](https://crates.io/crates/donglora-protocol)
+[![Docs.rs](https://docs.rs/donglora-protocol/badge.svg)](https://docs.rs/donglora-protocol)
 
-`no_std` by default. `defmt::Format` derives are opt-in via the default
-`defmt` feature. Host consumers disable default features:
+Wire protocol types and COBS framing for [DongLoRa], shared between the
+firmware and host crates (`client-rs`, `mux-rs`, `bridge`). `no_std`,
+zero-alloc, fixed-width little-endian — see the firmware repo's
+[`PROTOCOL.md`][protocol-md] for the full spec.
+
+[DongLoRa]: https://github.com/donglora
+[protocol-md]: https://github.com/donglora/firmware/blob/main/PROTOCOL.md
+
+## Install
 
 ```toml
+# Embedded / firmware (defmt::Format derives on by default):
+donglora-protocol = "0.1"
+
+# Host (no defmt):
 donglora-protocol = { version = "0.1", default-features = false }
 ```
 
-## Status
-
-Pre-1.0. Currently consumed by path dep; will publish to crates.io once
-the surface area settles.
-
 ## Layout
 
-- `src/lib.rs` — `Command`, `Response`, `RadioConfig`, `ErrorCode`, etc.
-- `src/framing.rs` — `CobsDecoder` + `cobs_encode_response` for USB/UART
-  transports.
-- `tests/` — proptest suite (roundtrips, bounded-capacity invariants,
-  regional-regs, duty-cycle math).
-- `fuzz/` — cargo-fuzz targets on the parser and framer.
+- `src/lib.rs` — `Command`, `Response`, `RadioConfig`, `Bandwidth`,
+  `ErrorCode` plus constants and validation/resolve helpers.
+- `src/framing.rs` — `CobsDecoder` (streaming) and `cobs_encode_response`.
+
+## Features
+
+| Feature | Default | What it does |
+|---------|---------|--------------|
+| `defmt` | yes | Derive `defmt::Format` on public enums. |
+| `std`   | no  | Enable `Debug`-based niceties for host-side fuzz / proptest. |
+
+## Testing
+
+The crate ships its own quality gate via `just test`:
+
+| Gate | What runs |
+|------|-----------|
+| `test-unit` | nextest across all feature permutations + doc tests |
+| `test-clippy` | `-D warnings` across all feature permutations |
+| `test-fmt` | `cargo fmt -- --check` |
+| `test-doc` | `cargo doc --no-deps --all-features` |
+| `test-deny` | `cargo deny check` |
+| `test-fuzz` | 60 s on each of 7 cargo-fuzz targets (nightly) |
+| `test-miri` | miri on lib + vector tests, both feature shapes (nightly) |
+| `test-mutants` | cargo-mutants under both feature configurations |
+
+The proptest suite alone exercises ~1.13M test cases per run.
+
+## License
+
+MIT — see [`LICENSE`](LICENSE).