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/facts_vs_positions/transcript.txt

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+Hannah: The pilot survey closed yesterday with 42 responses.
+
+Leo: The average rating was 3.8 out of 5.
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+Marta: I think that is weaker than it looks.
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+Leo: Why?
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+Marta: Because three enterprise customers skipped the survey entirely.
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+Hannah: That part is true. Northwind, Verdan, and Eastport did not respond.
+
+Leo: I still feel the pilot is healthy.
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+Marta: I disagree. My view is that we should slow down the rollout.
+
+Hannah: Let's capture both views and not decide rollout speed today.
+
+Leo: Okay, that matches my notes.