Add eval harness + Tier 2/3 mode template pages

### eval/ (scenario-based evaluation)

Complements the unit tests under test/basic. Scenarios fluctuate inputs
over simulated time, record every tick to JSONL, print a summary
table + event log, and check expectations. Complementary to unit
tests — these answer "how does the system respond to this input
profile" rather than "is this function correct".

- eval/run.js             — driver; monkey-patches Date.now so the
                            volume integrator ticks at 1 s/iter
                            regardless of wall-clock
- eval/scenarios/         — one file per scenario
  - levelbased-steady.js  — constant inflow, demand converges
  - levelbased-storm.js   — inflow surge, demand saturates
  - safety-dry-run-trip.js — manual mode, empty basin, safety trips
- eval/formatters/table.js — ASCII summary of sampled ticks
- eval/logs/              — per-scenario JSONL output (one line per tick)
- eval/README.md          — usage + scenario file shape + how to pipe
                            into InfluxDB/Grafana

All three starter scenarios PASS with their expectations.

### wiki/modes/ (tier template pages)

The levelbased page templated Tier-1 modes (static transfer function).
Added worked examples for the other two tiers so all mode pages share
a common skeleton and new modes have something concrete to imitate:

- flowbased.md   — Tier 2 (PID on measured outflow)
- powerbased.md  — Tier 2 (levelbased curve clipped by grid power budget)
- mpc.md         — Tier 3 (optimisation + forecast; block diagram +
                           scenario time-series instead of a fixed curve)

- modes/README.md — updated with the three-tier classification table
                    and diagram-type-per-tier guidance

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

eval/scenarios/levelbased-steady.js

@@ -0,0 +1,60 @@
+// Steady sewer inflow, level-based control, pumps should settle.
+//
+// Expectation: with a stable inflow of 0.008 m³/s and a pump bank with
+// max capacity 0.012 m³/s, the level settles in the RAMP zone (between
+// startLevel and maxLevel) at roughly the point where demand matches
+// inflow. No safety trips should fire.
+
+module.exports = {
+  name: 'levelbased-steady',
+  description: 'Constant sewer inflow below pump capacity; level converges inside the RAMP zone with demand matching inflow.',
+  durationSec: 1200,
+
+  config: {
+    general: { name: 'EvalSteady', id: 'eval-steady', 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: 98,
+      timeleftToFullOrEmptyThresholdSeconds: 0,
+    },
+  },
+
+  setup: async (ps) => {
+    // Stub MGC: its pumps collectively deliver (demand/100) × MAX_OUTFLOW.
+    const MAX_OUTFLOW = 0.012;  // m³/s
+    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 (_source, 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(2.0);  // start at the bottom of the RAMP zone
+  },
+
+  inputs: (t, ps) => {
+    ps.setManualInflow(0.008, Date.now(), 'm3/s');  // ≈ 29 m³/h
+  },
+
+  expectations: [
+    { name: 'no safety trips', type: 'safety_trips_eq', value: 0 },
+    { name: 'level stays below overflow', type: 'max_level_bounded', value: 4.5 },
+    { name: 'level stays above outflow', type: 'min_level_bounded', value: 0.2 },
+    { name: 'no threshold issues on init', type: 'threshold_issues_eq', value: 0 },
+  ],
+};