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/v0.1.0/12-payload-control.md

@@ -0,0 +1,68 @@
+# MeshCore Protocol Specification
+
+## Section 12: Payload — Control
+
+### Overview
+
+The CONTROL payload carries control and discovery data. Control packets are raw
+byte payloads whose structure is determined by the first byte. A subset of
+control packets (those with bit 7 of the first byte set) are restricted to
+zero-hop delivery only.
+
+### Payload Type
+
+Header payload type field: `0x0B` (CONTROL)
+
+### Wire Format
+
+```
+ 0
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+|  Control Byte |  Data...      |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+```
+
+### Fields
+
+| Field | Offset | Size | Type | Description |
+|-------|--------|------|------|-------------|
+| control_byte | 0 | 1 byte | uint8 | Control type identifier |
+| data | 1 | variable | raw | Control-specific data |
+
+### Zero-Hop Restriction
+
+When bit 7 (`0x80`) of the control byte is set, the packet is restricted to
+zero-hop delivery only. The reference implementation enforces this:
+
+- If `(payload[0] & 0x80) != 0` AND the packet is direct-routed:
+  - It is processed only if `getPathHashCount() == 0`.
+  - It is NOT forwarded to other nodes.
+
+### Discovery Protocols
+
+Control packets are commonly used for node discovery. The specific sub-protocol
+formats are application-defined, but typically include:
+
+- **Discovery Request**: Sent zero-hop to find nearby nodes
+- **Discovery Response**: Contains node type, name, SNR, and other metadata
+
+### Encoding
+
+1. Construct the raw control data bytes.
+2. If the control packet should be zero-hop only, set bit 7 of the first byte.
+3. Copy data to payload, set payload_len.
+
+### Constraints
+
+- Payload MUST be at least 1 byte (the control byte).
+- Maximum payload: 184 bytes (MAX_PACKET_PAYLOAD).
+
+### Cross-References
+
+- [Section 17: Routing](17-routing.md) — Zero-hop delivery
+- Test vectors: `corpus/payloads/control/`
+
+### Reference Implementation
+
+- `Mesh::createControlData()` in `src/Mesh.cpp` — Encoding
+- `Mesh::onRecvPacket()`, CONTROL handling — Zero-hop check and delivery