Matrix intake: main-timeline nudge, clearer messages, note text in grid

Four bot-side UX fixes surfaced by the live smoke:
- Post a brief pointer in the main timeline (a reply to the user's message)
  alongside the in-thread proposal card, so proposals aren't missed inside a
  thread. Pointer only — approvals still happen in the thread, where the note
  is visible (you can't make an informed yes/no without seeing it).
- A bare yes/no typed in the main timeline while a proposal is pending now
  gets a "reply in the thread" redirect instead of "couldn't tell what to record."
- Clearer commit confirmations: "Created a new grid entry for X" vs
  "Logged a note on X (existing grid entry)."
- Send a blank communication subject when a note is present so the grid's
  one-line note summary shows the note text, not the "(Matrix)" label
  (provenance stays in source="matrix_intake").

backend/matrix_intake/test_proposals.py

@@ -22,6 +22,15 @@ def test_store_put_get_pop():
     assert s.pop("$missing") is None
 
 
+def test_store_any_pending():
+    s = proposals.ProposalStore()
+    assert not s.any_pending()
+    s.put("$r", SAMPLE)
+    assert s.any_pending()
+    s.pop("$r")
+    assert not s.any_pending()
+
+
 def test_interpret_yes_variants():
     for t in ("yes", "Y", "approve", "  ok ", "👍"):
         assert proposals.interpret_reply(t)[0] == "approve", t
@@ -87,6 +96,15 @@ def test_render_meeting_note_variant():
     assert "meeting note" in proposals.render(note).lower()
 
 
+def test_summary_line_new_vs_note():
+    new_line = proposals.summary_line(SAMPLE)
+    assert "Acme Capital" in new_line and "new investor" in new_line.lower()
+    note_line = proposals.summary_line(dict(SAMPLE, intent="meeting_note"))
+    assert "Acme Capital" in note_line and "meeting note" in note_line.lower()
+    # the nudge must point the user to the thread, where the actual action lives
+    assert "thread" in new_line.lower()
+
+
 if __name__ == "__main__":
     fns = [v for k, v in sorted(globals().items()) if k.startswith("test_") and callable(v)]
     for fn in fns: