Allow channel sender names of up to 31 characters

The firmware keeps a node name in 32 bytes, but the sender prefix and the @[Name]
mention matched only 20 characters. A longer name stayed in the body: the transcript
showed no sender for it, and its reactions showed as new messages. Found on hardware
with "Hazelwood r0b3.Anduril" (22 characters).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

meshterm/core/channels.py

@@ -35,17 +35,21 @@ from urllib.parse import parse_qs, quote, urlsplit
 # not one time for each candidate channel. Thus the reception path pays almost nothing.
 
 #: Matches the ``Name: message`` convention that channel senders use to identify themselves
-#: (the protocol has no sender field). The name is 1–20 characters that are not colons, and
+#: (the protocol has no sender field). The name is 1–31 characters that are not colons, and
 #: ``": "`` must follow it. This rule is strict enough that it does not match ``http://…``
-#: or ``note:x``.
-SENDER_PREFIX = re.compile(r"^([^\s:][^:]{0,19}):[ \t]+(.*)$", re.DOTALL)
+#: or ``note:x``. The firmware keeps a node name in 32 bytes with its terminator, so 31 is
+#: the longest name that a sender can have. A limit of 20 left
+#: a longer name in the body. Then the transcript showed no sender for it, and a reaction
+#: from it did not read as a reaction.
+SENDER_PREFIX = re.compile(r"^([^\s:][^:]{0,30}):[ \t]+(.*)$", re.DOTALL)
 
 #: Matches an ``@[Name]`` mention token, which the reply flow puts into the compose line in
 #: advance. A transcript renders each token as a bare ``@Name`` in the hue of that sender,
 #: and does not show the brackets. The history face of the CLI also takes out the same
 #: names. Thus the token is defined here, with the remainder of the message-body parsing, and
-#: not in one of the two renderers. The name is 1–20 characters that are not ``]``.
-MENTION = re.compile(r"@\[([^\]]{1,20})\]")
+#: not in one of the two renderers. The name is 1–31 characters that are not ``]``, the
+#: same limit as :data:`SENDER_PREFIX`.
+MENTION = re.compile(r"@\[([^\]]{1,31})\]")
 
 
 def split_channel_sender(text: str) -> tuple[str | None, str]:

tests/test_reactions.py

@@ -393,3 +393,18 @@ def test_the_messages_list_previews_a_reaction_in_words() -> None:
     assert "Bob" in preview and "reacted 👍" in preview and "@[" not in preview
     ours = ChatMessage(text=reactions.direct_text("😂", "hi", _T), outbound=True)
     assert "reacted 😂" in _preview_text(ours, lambda name: None).plain
+
+
+def test_a_reaction_from_a_node_with_a_long_name_folds() -> None:
+    """A node name can have 31 characters. A sender of 22 is still split off its reaction.
+
+    The two messages are from the hardware log that found the fault: the name limit was 20,
+    so the reaction of ``Hazelwood r0b3.Anduril`` showed as a new message.
+    """
+    fold = ReactionFold(channel=True)
+    target = _channel("Hazelwood: ⚽ Union 2-1 at Chicago Fire (59')", 1_792_029_645)
+    fold.take(target)
+    react = _channel("Hazelwood r0b3.Anduril: @[Hazelwood]🔥\nmzjsjjpk", 1_792_029_654)
+    assert fold.take(react) is True
+    (badge,) = fold.badges(target)
+    assert badge.emoji == "🔥" and badge.reactors == [reactions.Reactor("Hazelwood r0b3.Anduril")]