Rename eval/ → simulations/ and fix log-write bug

Per discussion: "test" and "eval" overlap in meaning; "simulations"
is more honest about what's actually happening — scripted plant
inputs driving a physics sim, then recorded for analysis.

Rename scope:
- eval/ → simulations/ (tracked as git renames)
- Internal references in run.js and README.md updated
- wiki/modes/mpc.md link updated

Also fixes a log-write bug noticed during the rename:
- run.js didn't mkdir simulations/logs/ before createWriteStream,
  so the stream opened into a potentially non-existent dir and the
  file never materialised. Added fs.mkdirSync(..., recursive:true).
- end() wasn't awaited, so the process could exit before the stream
  flushed. Now awaits the 'finish' event. Confirmed: 1200 records
  actually land in simulations/logs/<scenario>.jsonl.
- Added simulations/logs/.gitignore so future JSONL artefacts stay
  out of the repo but the dir remains tracked.

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

simulations/scenarios/levelbased-storm.js

@@ -0,0 +1,60 @@
+// Storm surge — inflow triples briefly, pumps should saturate at 100%,
+// level rises toward overflow then recedes.
+//
+// Expectation: during the surge (t=300..600), demand reaches 100% and
+// level may transiently climb above maxLevel. Overflow safety should
+// fire if the surge overwhelms pump capacity; dry-run should not fire.
+
+module.exports = {
+  name: 'levelbased-storm',
+  description: 'Sewer inflow triples from 0.008 → 0.024 m³/s for 5 minutes then returns to baseline. Overfill safety may engage.',
+  durationSec: 1500,
+
+  config: {
+    general: { name: 'EvalStorm', id: 'eval-storm', unit: 'm3/h',
+      logging: { enabled: false, logLevel: 'error' } },
+    functionality: { softwareType: 'pumpingStation', role: 'stationcontroller', positionVsParent: 'atEquipment' },
+    basin: { volume: 50, height: 5, inflowLevel: 3, outflowLevel: 0.2, overflowLevel: 4.5 },
+    hydraulics: { refHeight: 'NAP', basinBottomRef: 0, minHeightBasedOn: 'outlet' },
+    control: {
+      mode: 'levelbased',
+      allowedModes: new Set(['levelbased']),
+      levelbased: { minLevel: 1, startLevel: 2, maxLevel: 4 },
+    },
+    safety: {
+      enableDryRunProtection: true,
+      dryRunThresholdPercent: 2,
+      enableOverfillProtection: true,
+      overfillThresholdPercent: 95,
+      timeleftToFullOrEmptyThresholdSeconds: 0,
+    },
+  },
+
+  setup: async (ps) => {
+    const MAX_OUTFLOW = 0.012;  // m³/s pumps cannot keep up with 3× surge
+    ps.machineGroups['mgc1'] = {
+      config: { general: { name: 'mgc1' } },
+      turnOffAllMachines: () => {
+        ps.measurements.type('flow').variant('predicted').position('out').child('mgc1').value(0, Date.now(), 'm3/s');
+      },
+      handleInput: async (_src, demand) => {
+        const d = Math.max(0, Math.min(100, Number(demand) || 0));
+        const outflow = (d / 100) * MAX_OUTFLOW;
+        ps.measurements.type('flow').variant('predicted').position('out').child('mgc1').value(outflow, Date.now(), 'm3/s');
+      },
+    };
+    ps.calibratePredictedLevel(2.5);
+  },
+
+  inputs: (t, ps) => {
+    const surge = (t >= 300 && t < 600) ? 0.024 : 0.008;
+    ps.setManualInflow(surge, Date.now(), 'm3/s');
+  },
+
+  expectations: [
+    { name: 'dry-run never trips', type: 'end_state_eq', field: 'safetyActive', value: false },
+    // Level may exceed maxLevel transiently but must stay under basinHeight
+    { name: 'level never breaches physical basin', type: 'max_level_bounded', value: 5.0 },
+    { name: 'demand saturates at 100% during surge', type: 'max_demand_bounded', value: 100 },
+  ],
+};