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_negative/transcript.txt

@@ -0,0 +1,19 @@
+Paula: The customer export takes longer than I expected.
+
+Ravi: Someone should probably look at it.
+
+Sam: Yes, maybe after the release freeze.
+
+Paula: I don't have capacity this week.
+
+Ravi: Same here.
+
+Sam: Then let's just keep it on the risk list.
+
+Paula: Right, no owner for now.
+
+Ravi: We can revisit it in planning.
+
+Sam: Okay.
+
+Paula: Next item.