feat: HomeFormatter parses inline entity tags instead of tool_end blocks

The supervisor LLM now embeds <type>[id1,id2]</type> entity tags in its
response text. The HomeFormatter buffers streamed tokens, detects complete
tags across chunk boundaries, and emits WsStreamBlock with entity type +
specific IDs. This replaces the old approach of emitting blocks for every
tool_end event, which dumped ALL entities regardless of relevance.

Also fixes:
- NoneType guard on metadata in _run_graph_stream (metadata can be None)
- Updated _HOME_SYSTEM prompt with entity tag instructions
- Updated all affected tests

tests/test_output_formatter.py

@@ -32,7 +32,7 @@ async def collect(formatter, event_stream):
 # ── HomeFormatter ─────────────────────────────────────────────────────────────
 
 @pytest.mark.asyncio
-async def test_home_formatter_text_token():
+async def test_home_formatter_plain_text():
     req_id = "req-1"
     events = [
         ("token", "Hello world"),
@@ -49,11 +49,11 @@ async def test_home_formatter_text_token():
 
 
 @pytest.mark.asyncio
-async def test_home_formatter_entity_ref_from_tool_end():
+async def test_home_formatter_entity_tag_single_id():
+    """A <project>[id]</project> tag emits a WsStreamBlock with entity + ids."""
     req_id = "req-2"
     events = [
-        ("tool_end", {"name": "task_agent", "result": "Found 3 tasks."}),
-        ("token", "Here are your tasks."),
+        ("token", "Here is your project:\n<project>[abc-123]</project>\nAll good."),
         ("mutations", []),
     ]
     formatter = HomeFormatter(request_id=req_id)
@@ -62,27 +62,86 @@ async def test_home_formatter_entity_ref_from_tool_end():
     block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
     assert len(block_frames) == 1
     assert block_frames[0].block_type == "entity_ref"
-    assert block_frames[0].data["entity"] == "tasks"
-    assert block_frames[0].data["result"] == "Found 3 tasks."
+    assert block_frames[0].data["entity"] == "projects"
+    assert block_frames[0].data["ids"] == ["abc-123"]
+
+    # Surrounding text is streamed
+    text = "".join(f.chunk for f in frames if isinstance(f, WsStreamText))
+    assert "Here is your project:" in text
+    assert "All good." in text
+    # The raw tag itself should NOT appear in streamed text
+    assert "<project>" not in text
 
 
 @pytest.mark.asyncio
-async def test_home_formatter_unknown_agent_no_block():
+async def test_home_formatter_entity_tag_multiple_ids():
     req_id = "req-3"
     events = [
-        ("tool_end", {"name": "unknown_agent", "result": "stuff"}),
+        ("token", "Pending:\n<task>[id-1,id-2,id-3]</task>"),
         ("mutations", []),
     ]
     formatter = HomeFormatter(request_id=req_id)
     frames = await collect(formatter, _stream(*events))
 
     block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
-    assert len(block_frames) == 0  # unknown agent → no entity mapping
+    assert len(block_frames) == 1
+    assert block_frames[0].data["entity"] == "tasks"
+    assert block_frames[0].data["ids"] == ["id-1", "id-2", "id-3"]
+
+
+@pytest.mark.asyncio
+async def test_home_formatter_multiple_entity_tags():
+    req_id = "req-4"
+    events = [
+        ("token", "<project>[p1]</project>\nText\n<task>[t1,t2]</task>"),
+        ("mutations", []),
+    ]
+    formatter = HomeFormatter(request_id=req_id)
+    frames = await collect(formatter, _stream(*events))
+
+    block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
+    assert len(block_frames) == 2
+    entities = {b.data["entity"] for b in block_frames}
+    assert entities == {"projects", "tasks"}
+
+
+@pytest.mark.asyncio
+async def test_home_formatter_tag_split_across_tokens():
+    """Entity tag arrives across two token chunks — still detected."""
+    req_id = "req-5"
+    events = [
+        ("token", "See: <project>[abc-"),
+        ("token", "123]</project> done"),
+        ("mutations", []),
+    ]
+    formatter = HomeFormatter(request_id=req_id)
+    frames = await collect(formatter, _stream(*events))
+
+    block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
+    assert len(block_frames) == 1
+    assert block_frames[0].data["entity"] == "projects"
+    assert block_frames[0].data["ids"] == ["abc-123"]
+
+
+@pytest.mark.asyncio
+async def test_home_formatter_tool_end_ignored():
+    """tool_end events no longer produce blocks — only entity tags do."""
+    req_id = "req-6"
+    events = [
+        ("tool_end", {"name": "task_agent", "result": "3 tasks"}),
+        ("token", "No tags here."),
+        ("mutations", []),
+    ]
+    formatter = HomeFormatter(request_id=req_id)
+    frames = await collect(formatter, _stream(*events))
+
+    block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
+    assert len(block_frames) == 0
 
 
 @pytest.mark.asyncio
 async def test_home_formatter_mutations_in_stream_end():
-    req_id = "req-4"
+    req_id = "req-7"
     muts = [{"action": "insert", "table": "tasks", "data": {"id": "t1"}}]
     events = [
         ("token", "Done"),
@@ -100,31 +159,13 @@ async def test_home_formatter_mutations_in_stream_end():
 @pytest.mark.asyncio
 async def test_home_formatter_frame_order():
     """stream_start is first, stream_end is last."""
-    req_id = "req-5"
+    req_id = "req-8"
     formatter = HomeFormatter(request_id=req_id)
     frames = await collect(formatter, _stream(("token", "Hi"), ("mutations", [])))
     assert isinstance(frames[0], WsStreamStart)
     assert isinstance(frames[-1], WsStreamEnd)
 
 
-@pytest.mark.asyncio
-async def test_home_formatter_multiple_tool_ends():
-    req_id = "req-6"
-    events = [
-        ("tool_end", {"name": "task_agent", "result": "3 tasks"}),
-        ("tool_end", {"name": "project_agent", "result": "2 projects"}),
-        ("token", "Overview done."),
-        ("mutations", []),
-    ]
-    formatter = HomeFormatter(request_id=req_id)
-    frames = await collect(formatter, _stream(*events))
-
-    block_frames = [f for f in frames if isinstance(f, WsStreamBlock)]
-    assert len(block_frames) == 2
-    entities = {b.data["entity"] for b in block_frames}
-    assert entities == {"tasks", "projects"}
-
-
 # ── FloatingFormatter ─────────────────────────────────────────────────────────
 
 @pytest.mark.asyncio