Establish prompt engineering baseline with Gold Standard tests

- introduce Gold Standard evaluation corpus
- document decision taxonomy
- define prompt-engineering methodology
- add regression workflow
- establish Prompt Version 2 baseline
- validate decision_simple, decision_deferred and decision_none

tests/gold/todo_simple/expected.json

@@ -0,0 +1,20 @@
+{
+  "facts": [
+    {
+      "fact": "The beta signup page points to the old privacy note.",
+      "evidence": "Omar: The beta signup page still points to the old privacy note."
+    }
+  ],
+  "decisions": [],
+  "todos": [
+    {
+      "task": "Update the privacy link on the beta signup page.",
+      "responsible": "Nina",
+      "deadline": "Thursday noon",
+      "evidence": "Nina: Yes, I will update the privacy link by Thursday noon."
+    }
+  ],
+  "questions": [],
+  "positions": [],
+  "technical": []
+}