A/B: Coverage & Decision Gate — Learn vs Act Routing

Same coverage_query tool, two implementation tasks: A asks about WebHost.Systems auth (coverage 0.486, 5 knowledge gaps) and gets a learn recommendation; B asks about Graphonomous MCP deployment (coverage 0.460) and also needs more knowledge. The act threshold requires coverage ≥0.720 and uncertainty ≤0.350 — both tasks fall short. A hypothetical review_goal shows what happens when the gate opens.