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/README.md

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+# todo_negative
+
+Tests that vague "someone should" language is not an action item.
+
+The transcript contains a real decision to keep the issue on the risk list, but no assigned task.
+
+Typical LLM mistakes:
+
+- Creating a todo with "someone" as owner.
+- Assigning Paula, Ravi, or Sam even though they explicitly do not take ownership.
+- Ignoring the explicit "no owner for now" correction.

tests/gold/todo_negative/expected.json

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+{
+  "facts": [
+    {
+      "fact": "The customer export takes longer than Paula expected.",
+      "evidence": "Paula: The customer export takes longer than I expected."
+    },
+    {
+      "fact": "There is no owner for the customer export issue for now.",
+      "evidence": "Paula: Right, no owner for now."
+    }
+  ],
+  "decisions": [
+    {
+      "decision": "The customer export issue will stay on the risk list for now.",
+      "evidence": "Sam: Then let's just keep it on the risk list. Paula: Right, no owner for now."
+    }
+  ],
+  "todos": [],
+  "questions": [],
+  "positions": [],
+  "technical": []
+}

tests/gold/todo_negative/transcript.txt

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+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.