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_editor_saved_observation.py

@@ -0,0 +1,24 @@
+import json
+
+from src.clean_agent_preview import preview_tool_result_text
+
+
+def test_successful_edit_exposes_saved_source_not_old_find():
+    observation = json.loads(preview_tool_result_text(
+        {'doc_id': 'fixture', 'applied': 1, 'version': 2, 'content': 'new wording'},
+        'edit_document', {'edits': [{'find': 'old wording', 'replace': 'new wording'}]},
+    ))
+    assert observation['current_content'] == 'new wording'
+    assert observation['version'] == 2
+    assert 'Saved source' in observation['content_state']
+
+
+def test_large_edit_observation_keeps_partial_failure_details():
+    observation = json.loads(preview_tool_result_text(
+        {'doc_id': 'fixture', 'applied': 1, 'content': 'a' * 10000,
+         'partial': True, 'rejected': 1, 'invalid_edits': [{'number': 2}]},
+        'edit_document', {},
+    ))
+    assert 'current_content' not in observation
+    assert observation['invalid_edits'] == [{'number': 2}]
+    assert 'Retry only' in observation['instruction']