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/proposals.py

@@ -36,6 +36,9 @@ class ProposalStore:
     def has(self, thread_root):
         return thread_root in self._pending
 
+    def any_pending(self):
+        return bool(self._pending)
+
 
 def _parse_edit(text):
     """Parse 'edit field=value' (also 'field: value'); return (canonical_field, value) or None."""
@@ -101,3 +104,11 @@ def render(proposal):
     lines.append("")
     lines.append("Reply **yes** to commit, **edit field=value** to change a field, or **no** to discard.")
     return "\n".join(lines)
+
+
+def summary_line(proposal):
+    """A brief one-liner for the main-timeline nudge; the full card lives in the thread."""
+    name = proposal.get("investor_name") or proposal.get("contact_name") or "?"
+    if proposal.get("intent") == "meeting_note":
+        return f"📝 Proposed a meeting note for **{name}** — see the thread to review & approve."
+    return f"📇 Proposed a new investor: **{name}** — see the thread to review & approve."