Advertise natural-language edits on the intake approval card

The in-thread approval handler already routes any reply that isn't yes/no/
edit-grammar through local Qwen (parse.revise), but the card copy only mentioned
'edit field=value', so the natural-language path was undiscoverable. Lead with
plain-words edits; the deterministic field=value fast-path still works.

backend/matrix_intake/proposals.py

@@ -180,7 +180,8 @@ def render(proposal):
         if val:
             lines.append(f"· {label}: {val}")
     lines.append("")
-    lines.append("Reply **yes** to commit, **edit field=value** to change a field, or **no** to discard.")
+    lines.append("Reply **yes** to commit, **no** to discard, or just tell me what to change in "
+                 "plain words (e.g. \"change the email to a@b.com\", \"the firm is Acme Capital\").")
     return "\n".join(lines)