Preserve preview harness, editor, email and task improvements

Snapshot current maintainer-preview application changes and regression fixtures for integration into lab. Excludes local runtime data, evaluation outputs and source backups. Focused Python regression selection: 140 passed; full suite not certified.

tests/test_buffered_terminal_answer.py

@@ -0,0 +1,49 @@
+import json
+from contextlib import asynccontextmanager
+
+import pytest
+
+from src import clean_agent_preview as runner
+from src.tool_policy import ToolPolicy
+from src.tool_schemas import FUNCTION_TOOL_SCHEMAS
+from src.turn_contract import requested_capabilities, selected_tools_for_request, resolve_turn_contract
+
+
+@pytest.mark.asyncio
+async def test_accepted_text_only_answer_is_emitted_after_required_tool_buffering(monkeypatch):
+    prompt = 'What time would that event start if it were pushed back by two hours? Do not change it.'
+    answer = 'It would start at 16:00 UTC.'
+
+    class Response:
+        def raise_for_status(self):
+            pass
+
+        async def aiter_lines(self):
+            yield 'data: ' + json.dumps({'choices': [{'delta': {'content': answer}}]})
+            yield 'data: [DONE]'
+
+    @asynccontextmanager
+    async def response(*args, **kwargs):
+        yield Response()
+
+    monkeypatch.setattr(runner, 'preview_model_response', response)
+    monkeypatch.setattr(runner, 'required_read_tool_choice', lambda *args, **kwargs: 'required')
+    policy = ToolPolicy()
+    selected = selected_tools_for_request(prompt)
+    contract = resolve_turn_contract(
+        capabilities=requested_capabilities(prompt), schemas=FUNCTION_TOOL_SCHEMAS,
+        policy=policy, selected_tools=selected, required_tools=selected or (), message=prompt,
+    )
+    events = []
+    async for chunk in runner.stream_preview(
+        endpoint_url='http://fixture', model='Ajax', headers={},
+        messages=[{'role': 'user', 'content': prompt}], turn_contract=contract,
+        session_id='fixture-buffered-answer', owner='fixture', disabled_tools=set(),
+        tool_policy=policy, thinking_mode='off', max_rounds=2,
+    ):
+        if chunk.startswith('data: ') and '[DONE]' not in chunk:
+            events.append(json.loads(chunk[6:]))
+    finals = [e['content'] for e in events if e.get('type') == 'final_response']
+    assert finals == [answer]
+    assert not any(e.get('delta') for e in events)
+    assert not any(e.get('type') == 'tool_start' for e in events)