feat(chat): stop an in-flight answer — Send becomes Stop, the partial is kept and persisted, the model stream is torn down

tests/unit/test_frontend_tool_states.py

@@ -53,15 +53,20 @@ def test_tool_branch_is_a_first_class_turn_branch() -> None:
 
 
 def test_calling_tool_label_strings() -> None:
-    """The 'calling tool' label strings the story keys off: the button
-    text and the status/typing-indicator labels. Phase 39 centralizes
-    the brand prefix: the name resolves from window.BOR_BRAND at call
-    time via brand() (the default name renders the same bytes)."""
+    """The 'calling tool' label strings the story keys off: the
+    status/typing-indicator labels. Phase 48 (owner-locked 2026-08-29)
+    revised the phase-37 contract: the button no longer relabels to
+    "Calling tool…" — it stays the enabled "Stop" control for the whole
+    in-flight turn (no sendLabel write in the branch); the calling-tool
+    status lives in #send-status + the typing-indicator aria-label only.
+    Phase 39 centralizes the brand prefix: the name resolves from
+    window.BOR_BRAND at call time via brand() (the default name renders
+    the same bytes)."""
     js = _js()
     tool_idx = js.find('ev.type === "tool"')
     delta_idx = js.find('ev.type === "delta"')
     branch = js[tool_idx:delta_idx]
-    assert '"Calling tool…"' in branch, "the button carries the calling-tool text"
+    assert "sendLabel" not in branch, "phase 48: the button keeps its Stop label"
     assert "`${brand()} is listing documents`" in branch
     assert "`${brand()} is reading ${argument}`" in branch
     assert "sendStatus.textContent = toolStatus" in branch, (