Send forwarded media to the forum topic picked in the share sheet

The picker only read the selected dialog ids, so media always landed in
a forum's General topic. Read ShareAlert's selectedDialogTopics as well
and address each target the way ShareAlert.sendInternal() does: reply to
the topic's start message in forums, or set monoForumPeer in a channel's
direct-messages chat.

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

tools/verify_bundle.py

@@ -463,6 +463,74 @@ def main(argv=None) -> int:
         f"got {links!r}",
     )
 
+    picker = ns.get("picker")
+    selected_targets = getattr(picker, "_selected_targets", None)
+    address = getattr(sender, "_address", None)
+    targets = None
+    addressed = None
+    if selected_targets is not None and address is not None:
+
+        class SparseArray:
+            def __init__(self, pairs):
+                self.pairs = pairs
+
+            def size(self):
+                return len(self.pairs)
+
+            def keyAt(self, i):
+                return self.pairs[i][0]
+
+            def valueAt(self, i):
+                return self.pairs[i][1]
+
+        class TopicMessageObject:
+            def __init__(self, account, message, generate_layout, check_media):
+                self.message = message
+                self.isTopicMainMessage = False
+
+        plain, forum, mono = object(), object(), object()
+        topic = types.SimpleNamespace(topicStartMessage="start-msg", from_id="user-peer")
+        mono_topic = types.SimpleNamespace(topicStartMessage="unused", from_id="dm-user")
+        alert = types.SimpleNamespace(
+            selectedDialogs=SparseArray([(11, plain), (-22, forum), (-33, mono)]),
+            selectedDialogTopics={forum: topic, mono: mono_topic},
+        )
+        messenger = sys.modules["org.telegram.messenger"]
+        saved = messenger.MessageObject
+        messenger.MessageObject = TopicMessageObject
+        messenger.DialogObject = types.SimpleNamespace(getPeerDialogId=lambda peer: 4242)
+        messenger.MessagesController = types.SimpleNamespace(
+            getInstance=lambda account: types.SimpleNamespace(isMonoForum=lambda d: d == -33)
+        )
+        try:
+            targets = selected_targets(alert, 0)
+        finally:
+            messenger.MessageObject = saved
+        params = [
+            address(types.SimpleNamespace(replyToMsg=None, replyToTopMsg=None, monoForumPeer=0), t)
+            for t in targets
+        ]
+        addressed = [
+            (
+                t.peer,
+                getattr(p.replyToTopMsg, "message", None),
+                p.replyToMsg is p.replyToTopMsg,
+                getattr(p.replyToTopMsg, "isTopicMainMessage", None),
+                p.monoForumPeer,
+            )
+            for t, p in zip(targets, params)
+        ]
+    check(
+        "selected forum topic is replied to; mono-forum topic sets monoForumPeer; plain chat untouched",
+        addressed
+        == [
+            (11, None, True, None, 0),
+            (-22, "start-msg", True, True, 0),
+            (-33, None, True, None, 4242),
+        ],
+        f"got {addressed!r}",
+    )
+
     media_at = getattr(ivmedia, "media_at", None)
     no_media = getattr(ivmedia, "NoMedia", None)
     raised = False