The Oxford comma, always, the one-line description included

Every list of three or more takes the serial comma: the one-liner in
pyproject.toml, meshterm/__init__.py, and --help ("USB, Bluetooth, or TCP",
"Windows, macOS, and Linux"), the README, the changelog, the manuals, the
issue and PR templates, and six strings the app shows (the region-name
rule, a repeater setting's help, the diagnostics tool's description, and
the archive confirms). The Windows-console notice is rewrapped so its
comma keeps it inside 72 columns.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -3,7 +3,7 @@
 # Split in two on purpose. Style is a property of the source, not of the machine, so
 # `lint` runs once and its failure is unambiguous. Behaviour is a property of the
 # machine, so `test` runs everywhere we claim to work — the description promises
-# Windows, macOS and Linux, and until this file existed that promise had only ever been
+# Windows, macOS, and Linux, and until this file existed that promise had only ever been
 # checked on one of them.
 name: CI