Show container state in look and inventory display

Containers now display their state when viewed:
- Closed containers show "(closed)"
- Open empty containers show "(open, empty)"
- Open containers with items show "(open, containing: item1, item2)"

This applies to both ground items in the look command and inventory items.
Added _format_thing_name helper to both look.py and things.py to handle
the display formatting consistently.

src/mudlib/commands/look.py

@@ -1,6 +1,7 @@
 """Look command for viewing the world."""
 
 from mudlib.commands import CommandDefinition, register
+from mudlib.commands.things import _format_thing_name
 from mudlib.effects import get_effects_at
 from mudlib.entity import Entity
 from mudlib.player import Player
@@ -106,7 +107,7 @@ async def cmd_look(player: Player, args: str) -> None:
         obj for obj in zone.contents_at(player.x, player.y) if isinstance(obj, Thing)
     ]
     if ground_items:
-        names = ", ".join(item.name for item in ground_items)
+        names = ", ".join(_format_thing_name(item) for item in ground_items)
         player.writer.write(f"On the ground: {names}\r\n")
 
     await player.writer.drain()

src/mudlib/commands/things.py

@@ -1,6 +1,7 @@
 """Get, drop, and inventory commands for items."""
 
 from mudlib.commands import CommandDefinition, register
+from mudlib.container import Container
 from mudlib.player import Player
 from mudlib.thing import Thing
 from mudlib.zone import Zone
@@ -32,6 +33,23 @@ def _find_thing_in_inventory(name: str, player: Player) -> Thing | None:
     return None
 
 
+def _format_thing_name(thing: Thing) -> str:
+    """Format a thing's name with container state if applicable."""
+    if not isinstance(thing, Container):
+        return thing.name
+
+    if thing.closed:
+        return f"{thing.name} (closed)"
+
+    # Container is open
+    contents = [obj for obj in thing.contents if isinstance(obj, Thing)]
+    if not contents:
+        return f"{thing.name} (open, empty)"
+
+    names = ", ".join(item.name for item in contents)
+    return f"{thing.name} (open, containing: {names})"
+
+
 async def cmd_get(player: Player, args: str) -> None:
     """Pick up an item from the ground."""
     if not args.strip():
@@ -86,7 +104,7 @@ async def cmd_inventory(player: Player, args: str) -> None:
 
     lines = ["You are carrying:\r\n"]
     for thing in things:
-        lines.append(f"  {thing.name}\r\n")
+        lines.append(f"  {_format_thing_name(thing)}\r\n")
 
     await player.send("".join(lines))
 

tests/test_container_display.py

@@ -74,9 +74,7 @@ async def test_look_shows_open_empty_container(player, test_zone, mock_writer):
 
 
 @pytest.mark.asyncio
-async def test_look_shows_open_container_with_contents(
+async def test_look_shows_open_container_with_contents(player, test_zone, mock_writer):
-    player, test_zone, mock_writer
-):
     """look shows open containers with their contents."""
     from mudlib.commands.look import cmd_look