refactor(webui): remove legacy session messages route

tests/agent/test_loop_save_turn.py

@@ -1074,9 +1074,8 @@ async def test_process_message_persists_media_paths_on_user_turn(tmp_path: Path)
     """User turns that attach images must record the media paths alongside
     the text so the webui can rehydrate previews on session replay.
 
-    This is the producer half of the signed-media-URL round-trip: paths are
-    stored here, then :meth:`WebSocketChannel._augment_media_urls` maps them
-    onto signed URLs on the way out.
+    The WebUI transcript replay can use these paths to restore attachment
+    previews when it backfills from canonical session history.
     """
     img_a = tmp_path / "uuid-1.png"
     img_a.write_bytes(_PNG_1X1)

tests/utils/test_subagent_channel_display.py

@@ -1,9 +1,6 @@
 """Tests for subagent announce text shaping on external channel surfaces."""
 
-from nanobot.utils.subagent_channel_display import (
-    scrub_subagent_announce_body,
-    scrub_subagent_messages_for_channel,
-)
+from nanobot.utils.subagent_channel_display import scrub_subagent_announce_body
 
 
 def test_scrub_subagent_keeps_header_and_result_only() -> None:
@@ -22,24 +19,6 @@ Summarize this naturally for the user. Keep it brief."""
     assert "Summarize" not in out
 
 
-def test_scrub_subagent_messages_mutates_matching_rows() -> None:
-    messages: list[dict] = [
-        {"role": "assistant", "content": "hi"},
-        {
-            "role": "assistant",
-            "content": (
-                "[Subagent 'x' completed successfully]\n\nTask: t\n\nResult:\nr\n\nSummarize this naturally"
-            ),
-            "injected_event": "subagent_result",
-        },
-    ]
-    scrub_subagent_messages_for_channel(messages)
-    assert messages[0]["content"] == "hi"
-    assert "Task:" not in messages[1]["content"]
-    assert "[Subagent 'x' completed successfully]" in messages[1]["content"]
-    assert "r" in messages[1]["content"]
-
-
 def test_scrub_normalizes_crlf_before_result_marker() -> None:
     raw = "[Subagent 'z' failed]\r\n\r\nTask: x\r\n\r\nResult:\r\none line\r\n\r\nSummarize this naturally"
     out = scrub_subagent_announce_body(raw)