The terminal-allocation audit settled the protocol's OSC number on 1717 (unused
by every surveyed terminal — see diff-line-metadata-osc-spec.md), retiring the
456 placeholder. Rename the host side to match: the gocui carrier that accumulates
and reads back the sequence, the parser, and the handshake env var the pager
subprocess is given (now EMIT_OSC1717_METADATA). Flip the design notes and spec
from 'rename pending' to done.
The delta and difftastic emitters are renamed in their own repos.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>