Docs + simulations refresh; align spill-flow keys with new position

- wiki/functional-description.md: rename Overfill Protection → High-volume
  Safety; tighten basin-ordering chain; relocate level-based mode
  diagrams under wiki/diagrams/modes/level-based/; document the new
  flow.predicted.overflow.default position (replaces the previous
  child='overflow' under position 'out'); add underflowVolume +
  predictedUnderflowVolume entries.
- wiki/modes/{levelbased,powerbased}.md: paragraph cleanups.
- wiki/diagrams: move level-linear basin diagram under modes/level-based/
  alongside a new level-log variant.
- simulations/run.js: add max_demand_gt expectation.
- simulations/scenarios/*: minor fixture updates.
- test/basic/nodeClass-config.test.js: new config-shape coverage.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

simulations/run.js

@@ -54,6 +54,10 @@ function evalExpectation(ex, records) {
       const v = Math.max(...demands);
       return { ok: v <= ex.value, msg: `max demand = ${v.toFixed(0)} % (bound: ≤ ${ex.value})` };
     }
+    case 'max_demand_gt': {
+      const v = Math.max(...demands);
+      return { ok: v > ex.value, msg: `max demand = ${v.toFixed(0)} % (expected > ${ex.value})` };
+    }
     case 'safety_trips_eq': {
       const n = records.filter((r) => r.safetyActive).length;
       return { ok: n === ex.value, msg: `${n} ticks with safetyActive (expected ${ex.value})` };