v1.4.26

chore: release v1.4.26

Bumps vsn to 1.4.26 for hex publish. Changelog entry covers the three
feature commits since v1.4.25: dist_relay_client + protocol module
(6e7954c), macula_dist.erl integration + public join_dist_relay/1 API
(6a4e2c3), and the CT-suite-driven bug fixes for async_accept_stream
+ orphan stream buffer + leftover bytes handoff (2180b30).

v1.4.25 can't be republished — hex.pm's 1-hour modification window
passed. This is the correct next semver (minor feature additions,
no breaking API changes).

After publish: pin demo (present-macula-dist) and infrastructure
compose to v1.4.26 where they currently use ~> 1.4 / main branch
checkouts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>