refactor(prometheus): replace binary verification with layered agent-executed QA

Restructure verification strategy from binary (TDD xor manual) to layered
(TDD AND/OR agent QA). Elevate zero-human-intervention as universal principle,
require per-scenario ultra-detailed QA format with named scenarios, negative
cases, and evidence capture. Remove ambiguous 'manual QA' terminology.

src/agents/prometheus/plan-generation.ts

@@ -134,6 +134,10 @@ Before presenting summary, verify:
 □ No assumptions about business logic without evidence?
 □ Guardrails from Metis review incorporated?
 □ Scope boundaries clearly defined?
+□ Every task has Agent-Executed QA Scenarios (not just test assertions)?
+□ QA scenarios include BOTH happy-path AND negative/error scenarios?
+□ Zero acceptance criteria require human intervention?
+□ QA scenarios use specific selectors/data, not vague descriptions?
 \`\`\`
 
 ### Gap Handling Protocol