release: v0.1.0

First cut release. Snapshots ./src/ as ./versions/v0.1.0/ via
`just cut-version v0.1.0` (22 files: 21 chapter MDs + SUMMARY.md).
Deployed alongside `latest` at:

  https://swaits.github.io/meshcore-spec/v0.1.0/

Also:

- CHANGELOG.md adopts Keep a Changelog-style version sections.
  Future entries land under [Unreleased] and graduate to a version
  heading when cut. The existing date-stamped pass entries stay
  put as a historical record of the work captured in v0.1.0.
- README.md fixes a stale "per vX.Y.Z tag" mention left over from
  the tag-based versioning model, and links the current release
  explicitly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

versions/v0.1.0/13-payload-raw-custom.md

@@ -0,0 +1,49 @@
+# MeshCore Protocol Specification
+
+## Section 13: Payload — Raw Custom
+
+### Overview
+
+The RAW_CUSTOM payload carries application-defined raw bytes with no prescribed
+structure. It is intended for applications that implement their own encryption,
+framing, or payload formats on top of the MeshCore transport.
+
+### Payload Type
+
+Header payload type field: `0x0F` (RAW_CUSTOM)
+
+### Wire Format
+
+```
+ 0
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+|     Raw Data (1-184 bytes)    |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+```
+
+### Fields
+
+| Field | Offset | Size | Type | Description |
+|-------|--------|------|------|-------------|
+| data | 0 | 1-184 bytes | raw | Application-defined payload |
+
+### Routing
+
+In the current reference implementation, RAW_CUSTOM packets are only processed
+when received via direct routing. They are NOT flood-routed.
+
+### Constraints
+
+- Payload MUST be at least 1 byte.
+- Maximum payload: 184 bytes (MAX_PACKET_PAYLOAD).
+- Maximum total data: limited by `sizeof(Packet::payload)` which is
+  MAX_PACKET_PAYLOAD (184).
+
+### Cross-References
+
+- Test vectors: `corpus/payloads/raw-custom/`
+
+### Reference Implementation
+
+- `Mesh::createRawData()` in `src/Mesh.cpp` — Encoding
+- `Mesh::onRecvPacket()`, case `PAYLOAD_TYPE_RAW_CUSTOM` — Processing (direct only)