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/decision_deferred/README.md

@@ -0,0 +1,21 @@
+# decision_deferred
+
+Tests that a process decision to defer a substantive decision is still extracted
+as a decision.
+
+The transcript contains several candidate options for the weekly dashboard, but
+the group does not choose any of them. Instead, Mira explicitly says not to
+decide today and Jonas agrees that more input is needed.
+
+Ground truth:
+
+- No substantive dashboard schedule decision is reached.
+- One process decision is reached: the substantive decision is deferred until
+  more information is available.
+
+Typical LLM mistakes:
+
+- Extracting Monday, Tuesday, or Friday as the chosen dashboard day.
+- Treating "I like shorter" as an approval.
+- Missing the deferral because the substantive decision is unresolved.
+- Treating "no decision today" as equivalent to no decision at all.