fix(command): explain empty dream runs

nanobot/command/builtin.py

@@ -326,7 +326,8 @@ async def cmd_dream(ctx: CommandContext) -> OutboundMessage:
             if result is None:
                 await loop.bus.publish_outbound(OutboundMessage(
                     channel=msg.channel, chat_id=msg.chat_id,
-                    content="Dream: nothing to process.",
+                    content=_format_dream_no_input_message(),
+                    metadata={"render_as": "text"},
                 ))
                 return
             prompt, last_cursor = result
@@ -374,6 +375,23 @@ async def cmd_dream(ctx: CommandContext) -> OutboundMessage:
     )
 
 
+def _format_dream_no_input_message() -> str:
+    return "\n".join([
+        "Dream has no conversation history to process yet.",
+        "",
+        "Dream reads new entries from `memory/history.jsonl` after the current Dream cursor.",
+        (
+            "Short chats only reach that file after token compaction or idle auto-compact, "
+            "so a fresh or short WebUI chat may leave Dream with no input."
+        ),
+        "",
+        "Next steps:",
+        "- Enable `agents.defaults.idleCompactAfterMinutes` so completed chats become Dream input automatically.",
+        "- Compact the current chat into memory once that manual action is available.",
+        "- If you expected history to exist, check whether `memory/history.jsonl` has new entries after the Dream cursor.",
+    ])
+
+
 def _extract_changed_files(diff: str) -> list[str]:
     """Extract changed file paths from a unified diff."""
     files: list[str] = []