Add DM support, friend identification, and target pruning

React in 1:1 DMs alongside servers/groups, surface the resolved friend
username at startup and in the stats panel, verify reactions actually
stick after adding them (with jump links for manual spot-checking),
and prune stale targets from stats on each run so only the currently
mutual set is shown.

bot/discovery.py

@@ -10,16 +10,27 @@ log = logging.getLogger(__name__)
 @dataclass
 class Target:
     target_id: int
-    target_type: str  # "guild" | "group_dm"
+    target_type: str  # "guild" | "group_dm" | "dm"
     name: str
 
 
-async def discover_targets(client: discord.Client, friend_id: int, manual_guild_ids: Optional[List[int]] = None) -> List[Target]:
+async def resolve_friend(client: discord.Client, friend_id: int) -> discord.User:
+    """Fetch the target user object so we can display who the script is
+    actually reacting to (helps catch a wrong/typo'd friend_id early)."""
+    user = client.get_user(friend_id)
+    if user is None:
+        user = await client.fetch_user(friend_id)
+    return user
+
+
+async def discover_targets(
+    client: discord.Client, friend: discord.User, manual_guild_ids: Optional[List[int]] = None
+) -> List[Target]:
+    friend_id = friend.id
     targets: List[Target] = []
     guild_ids_seen = set()
 
     try:
-        friend = client.get_user(friend_id) or await client.fetch_user(friend_id)
         profile = await friend.profile(with_mutual_guilds=True, with_mutual_friends=False, with_mutual_friends_count=False)
         for mutual in (profile.mutual_guilds or []):
             guild = client.get_guild(mutual.id)
@@ -44,6 +55,12 @@ async def discover_targets(client: discord.Client, friend_id: int, manual_guild_
         targets.append(Target(guild_id, "guild", name))
         guild_ids_seen.add(guild_id)
 
+    try:
+        dm_channel = friend.dm_channel or await friend.create_dm()
+        targets.append(Target(dm_channel.id, "dm", f"DM with {friend}"))
+    except discord.HTTPException:
+        log.warning("Failed to open the 1:1 DM channel with %s", friend, exc_info=True)
+
     for channel in client.private_channels:
         if isinstance(channel, discord.GroupChannel) and any(u.id == friend_id for u in channel.recipients):
             name = channel.name or ", ".join(u.name for u in channel.recipients)