First stable release of the Heidrun Hotline protocol package.

Ships HeidrunCore (wire types + Network.framework client), HeidrunNIOClient (cross-platform SwiftNIO client), and the heidrun CLI.

Capabilities negotiated via DATA_CAPABILITIES (0x01F0):

• Large-file transfers (>4 GiB) — 64-bit sizes, 24-byte HTXF handshake, 64-bit FFO fork headers; single-file and folder.
• UTF-8 text encoding — opt-in UTF-8 for all strings (chat, names, news, …); macOS Roman otherwise.

Plus Heidrun extensions (0xE000 band): emoji avatars, resource-fork framed downloads. Self-signed TLS, tracker registration/listing, news, file transfers.

The wire format is additive and backward-compatible: every extension degrades gracefully against peers that don't negotiate it. See docs/PROTOCOL-EXTENSIONS.md.