chore(contextual): purge residual floating WsFrame defs + output_formatter branch

After M6.5 deletion of run_floating_stream and the frame dispatch,
WsFrameType.floating_request/floating_domain, WsFloatingRequest,
WsFloatingDomain, WsFloatingScope, WsDomain, and the StreamFormatter's
floating_domain branch were left as dead protocol surface. Remove them,
along with the corresponding test cases in test_schemas_v3.py and
test_output_formatter.py.

app/core/output_formatter.py

@@ -6,7 +6,7 @@ import re
 from collections.abc import AsyncGenerator
 from typing import Any
 
-from app.schemas import WsFloatingDomain, WsStreamEnd, WsStreamStart, WsStreamText
+from app.schemas import WsStreamEnd, WsStreamStart, WsStreamText
 
 # Matches <canvas kind="...">...</canvas> blocks (single-line or multiline).
 _CANVAS_BLOCK_RE = re.compile(
@@ -31,7 +31,7 @@ def extract_canvas_block(text: str) -> tuple[str, str | None, str | None]:
     visible = visible.strip()
     return visible, canvas_content, canvas_kind
 
-WsFrame = WsStreamStart | WsStreamText | WsStreamEnd | WsFloatingDomain
+WsFrame = WsStreamStart | WsStreamText | WsStreamEnd
 
 
 class StreamFormatter:
@@ -47,14 +47,6 @@ class StreamFormatter:
         started = False
 
         async for event_type, data in event_stream:
-            if event_type == "floating_domain":
-                if isinstance(data, dict):
-                    yield WsFloatingDomain(
-                        request_id=self.request_id,
-                        domain=data,
-                    )
-                continue
-
             if event_type != "token":
                 continue