fix(bot): un-reacting from a poll never un-counted the vote

wyr/acronym/nhie/hottake tracked votes only on reaction-add, using
"add to bucket A, remove from bucket B" logic that self-corrects when
switching reactions but not when a reaction is simply removed — nio
never subscribed to RedactionEvent at all, so an un-react was
invisible to the bot. Fixes LotusGuild/matrix#6 (repro: react agree
and disagree, remove disagree, still counted as disagree).

Adds unrecord_* counterparts to each record_* vote function, a
reaction_id -> (poll_event_id, sender) index in Callbacks (only
populated for reactions on messages we're actually tracking, so it
stays bounded) so a later redaction can be traced back to what to
un-count, and wires up RedactionEvent -> callbacks.redaction in bot.py.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

matrixbot/callbacks.py

@@ -13,6 +13,14 @@ from commands import (
     record_acronym_vote,
     record_nhie_reaction,
     record_hottake_reaction,
+    unrecord_wyr_vote,
+    unrecord_acronym_vote,
+    unrecord_nhie_reaction,
+    unrecord_hottake_reaction,
+    _WYR_POLLS,
+    _ACRONYM_POLL_IDS,
+    _NHIE_POLLS,
+    _HOTTAKE_POLLS,
 )
 logger = logging.getLogger("matrixbot")
 
@@ -33,11 +41,25 @@ def handle_command_errors(func):
     return wrapper
 
 
+def _is_tracked_poll(event_id: str) -> bool:
+    return (
+        event_id in _WYR_POLLS
+        or event_id in _ACRONYM_POLL_IDS
+        or event_id in _NHIE_POLLS
+        or event_id in _HOTTAKE_POLLS
+    )
+
+
 class Callbacks:
     def __init__(self, client: AsyncClient):
         self.client = client
         # Track the sync token so we ignore old messages on startup
         self.startup_sync_token = None
+        # reaction event_id -> (poll message event_id, sender), so an
+        # un-react (m.room.redaction of the reaction) can be traced back to
+        # which poll/sender to remove — only populated for reactions on a
+        # message we're actually tracking, so it stays bounded.
+        self._reaction_index: dict[str, tuple[str, str]] = {}
 
     async def message(self, room, event):
         # Ignore messages from before the bot started
@@ -97,6 +119,8 @@ class Callbacks:
         record_acronym_vote(reacted_event_id, event.sender, key)
         record_nhie_reaction(reacted_event_id, event.sender, key)
         record_hottake_reaction(reacted_event_id, event.sender, key)
+        if _is_tracked_poll(reacted_event_id):
+            self._reaction_index[event.event_id] = (reacted_event_id, event.sender)
 
     async def unknown_event(self, room, event):
         """Fallback handler for UnknownEvent — catches any m.reaction not parsed by nio."""
@@ -120,6 +144,28 @@ class Callbacks:
         record_acronym_vote(reacted_event_id, event.sender, key)
         record_nhie_reaction(reacted_event_id, event.sender, key)
         record_hottake_reaction(reacted_event_id, event.sender, key)
+        if _is_tracked_poll(reacted_event_id):
+            self._reaction_index[event.event_id] = (reacted_event_id, event.sender)
+
+    async def redaction(self, room, event):
+        """Handle m.room.redaction — an un-react. Reaction adds are tracked
+        via `reaction`/`unknown_event` above; this is their counterpart so a
+        removed vote doesn't stay counted forever (it previously only
+        self-corrected when a user switched to a different reaction, not
+        when they simply removed one — see LotusGuild/matrix#6)."""
+        if self.startup_sync_token is None:
+            return
+
+        entry = self._reaction_index.pop(event.redacts, None)
+        if entry is None:
+            return
+        reacted_event_id, sender = entry
+        logger.info("reaction removed: target=%s sender=%s", reacted_event_id[:16], sender)
+
+        unrecord_wyr_vote(reacted_event_id, sender)
+        unrecord_acronym_vote(reacted_event_id, sender)
+        unrecord_nhie_reaction(reacted_event_id, sender)
+        unrecord_hottake_reaction(reacted_event_id, sender)
 
     async def member(self, room, event):
         """Handle m.room.member events.