fix: 3-level hierarchy in help paste output

Plugin name at column 0, command at indent 4, docstring at indent 8.
Single-command paste keeps command at 0, docstring at 4.
Only paste when actual docstring content exists.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_core.py

@@ -237,8 +237,8 @@ class TestHelpCommand:
         assert "!widget -- Manage widgets" in bot.replied[0]
         assert "https://" not in bot.replied[0]
 
-    def test_help_paste_body_indented(self):
-        """Paste body has command name flush-left, docstring indented."""
+    def test_help_cmd_paste_hierarchy(self):
+        """Single-command paste: header at 0, docstring at 4."""
         bot = _FakeBot()
         pastes: list[str] = []
         bot.registry._modules["flaskpaste"] = _make_fp_module(capture=pastes)
@@ -250,9 +250,39 @@ class TestHelpCommand:
         asyncio.run(_mod.cmd_help(bot, msg))
         assert len(pastes) == 1
         lines = pastes[0].split("\n")
-        # First line: command header, no indent
+        # Level 0: command header flush-left
         assert lines[0] == "!widget -- Manage widgets"
-        # Docstring lines are indented 4 spaces
+        # Level 1: docstring lines indented 4 spaces
         for line in lines[1:]:
             if line.strip():
                 assert line.startswith("    "), f"not indented: {line!r}"
+
+    def test_help_list_paste_hierarchy(self):
+        """Full reference paste: plugin at 0, command at 4, doc at 8."""
+        bot = _FakeBot()
+        pastes: list[str] = []
+        bot.registry._modules["flaskpaste"] = _make_fp_module(capture=pastes)
+        mod = types.ModuleType("core")
+        mod.__doc__ = "Core plugin."
+        bot.registry._modules["core"] = mod
+        bot.registry.commands["state"] = _FakeHandler(
+            name="state", callback=_cmd_with_doc,
+            help="Inspect state", plugin="core",
+        )
+        msg = _Msg(text="!help")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(pastes) == 1
+        text = pastes[0]
+        lines = text.split("\n")
+        # Level 0: plugin header
+        assert lines[0] == "[core]"
+        # Level 1: plugin description
+        assert lines[1] == "    Core plugin."
+        # Blank separator
+        assert lines[2] == ""
+        # Level 1: command header at indent 4
+        assert lines[3] == "    !state -- Inspect state"
+        # Level 2: docstring at indent 8
+        for line in lines[4:]:
+            if line.strip():
+                assert line.startswith("        "), f"not at indent 8: {line!r}"