Introduce shared evidence model and governance imports

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a070b5-4994-7271-bd8b-7c3dbcedec4b

src/info_tech_canon/generation.py

@@ -90,9 +90,10 @@ COMMON_DISTINCTIONS = [
     {
         "id": "policy-control-evidence",
         "title": "Policy vs Control vs Evidence",
-        "summary": "Policy states intent or rule, control implements or enforces that rule, and evidence records why the claim should be trusted.",
+        "summary": "Governance owns policy and control; ITC-EVID owns the distinct evidence assertion and its addressable source. Evidence supports a stated interest without guaranteeing truth.",
         "source_artifacts": [
             "model/governance",
+            "model/evidence",
             "model/security",
             "model/observability",
         ],