fix(levelBased): drop hold zone, route through MGC.setDemand, add holdLevel + integrator variant pick; slim npm pack

levelBased ramp + engagement:
- Ramp foot is now max(startLevel, holdLevel) — was max(startLevel,
  inflowLevel). inflowLevel is basin geometry, not a control setpoint;
  the implicit hold zone it created was causing pumps to "start at
  inflowLevel" instead of startLevel.
- New optional `holdLevel` config (defaults to startLevel = no hold band).
  When raised, pumps engage at startLevel and hold at 0 % = MGC flow.min
  across [startLevel, holdLevel], then ramp 0..100 % to maxLevel.
- Engagement decided in run() (not in `_applyMachineGroupLevelControl`):
  rising-edge hysteresis arming gates a clean turnOff early-return.
  Once armed, the helper always forwards setDemand(pct, '%') — 0 %
  legitimately means "engaged at min flow", no more soft-turnOff at
  the boundary.
- Disengagement paths (minLevel hard-stop, stopLevel falling-edge,
  pre-arming idle) now all clear the shifted-ramp hysteresis state too.
- Threshold validator drops the startLevel ≤ inflowLevel rule; adds
  startLevel ≤ holdLevel < maxLevel (only checked when holdLevel is
  explicitly set, so default-null doesn't false-flag).

MGC unit math:
- Replace direct group.handleInput(percent) with group.setDemand(pct, '%')
  in _applyMachineGroupLevelControl. The percent → m³/s resolution now
  lives in MGC.setDemand (committed separately in the MGC submodule).

FlowAggregator variant picking:
- New _pickFlowSum() helper mirrors selectBestNetFlow's variant
  precedence (measured first, then predicted) and resolves each side
  independently. Realistic mixed case — real measured upstream sensor +
  predicted pump outflow — now feeds the predicted-volume integrator.
  Was reading only `flow.predicted.*` so a real upstream sensor
  (which writes `flow.measured.*`) never moved the level.

Editor:
- New `holdLevel` and `deadZoneKeepAlivePercent` defaults + side-panel
  input rows in the levelbased mode preview.
- Add the missing `ps-mode-line-holdLevel` SVG marker (was declared in
  the side-panel coupling but the SVG element didn't exist, so the
  dashed line never rendered).
- Relax stopLevel marker gate so it renders for any non-negative typed
  value — start/stop ordering is the ribbon's job, not the marker's
  (was hiding the line whenever startLevel was momentarily smaller).
- Add holdLevel to the marker loop in mode-preview so changes track.
- Add stopLevel + holdLevel + maxLevel to all three bindRedraw lists
  (basin-diagram, mode-preview, bounds.apply) so the SVG, validation
  ribbon, and HTML5 min/max attrs update on every edit.
- Initialise stopLevel + holdLevel + deadZoneKeepAlivePercent inputs
  in oneditprepare so reopening the editor shows the saved values.
- nodeClass passes holdLevel + deadZoneKeepAlivePercent into the
  domain config.

Tests:
- New test/basic/_probe_upstream_emit.test.js: confirms the parent
  surfaces flow.measured.upstream.* on Port 0 after a measurement
  child write — pins the previously-invisible measured variant flow.
- flowAggregator.basic.test.js: two new regression cases — measured
  inflow when predicted side is empty, and the measured-in /
  predicted-out mixed case.
- control-levelBased.basic.test.js: new cases for the holdLevel hold
  band, the [stopLevel, startLevel] keep-alive, the engagement gate,
  and the "0 % at startLevel = setDemand" contract.
- specificClass.test.js: zone tests adjusted to the new ramp foot.
  Shifted-ramp tests pin holdLevel = 3 explicitly so their legacy
  arithmetic (ramp foot at inflowLevel) stays self-consistent.
- shifted-ramp-end-to-end.test.js: same holdLevel pin for the same
  reason.

Packaging:
- Add .gitignore + .npmignore so the published tarball drops the
  wiki/, simulations/, test/, tools/, .claude/ etc. The pack went
  from 1.5 MB (72 files) to ~57 KB (30 files).

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

src/measurement/flowAggregator.js

@@ -57,6 +57,32 @@ class FlowAggregator {
     this._predictedFlowState = { inflow: 0, outflow: 0, lastTimestamp: timestamp };
   }
 
+  // Pick the best-available variant for one side of the basin balance.
+  // Mirrors selectBestNetFlow's variant precedence (measured first, then
+  // predicted) but resolves each side independently — so a real measured
+  // upstream sensor + a predicted pump outflow both feed the integrator.
+  // Returns the summed flow at the requested positions. The first variant
+  // that has any registered measurement at one of those positions wins,
+  // even if its sum is 0 (a sensor that reads 0 is still data).
+  _pickFlowSum(positions, flowUnit = 'm3/s') {
+    const buckets = this.measurements.measurements?.flow;
+    if (!buckets) return { sum: 0, variant: null };
+    for (const variant of this.flowVariants) {
+      const variantBucket = buckets[variant];
+      if (!variantBucket) continue;
+      const hasAny = positions.some((pos) => {
+        const posBucket = variantBucket[pos];
+        return posBucket && Object.keys(posBucket).length > 0;
+      });
+      if (!hasAny) continue;
+      return {
+        sum: this.measurements.sum('flow', variant, positions, flowUnit) || 0,
+        variant,
+      };
+    }
+    return { sum: 0, variant: null };
+  }
+
   update() {
     const flowUnit = 'm3/s';
     const now = Date.now();
@@ -64,8 +90,13 @@ class FlowAggregator {
     // Synthetic spill flow lives at its OWN position ('overflow') —
     // not as a child of 'out'. That keeps it out of the operational
     // outflow sum here so no self-subtraction is needed.
-    const inflow = this.measurements.sum('flow', 'predicted', this.flowPositions.inflow, flowUnit) || 0;
-    const outflowReal = this.measurements.sum('flow', 'predicted', this.flowPositions.outflow, flowUnit) || 0;
+    // Inflow + outflow are resolved per-side: a real measured upstream
+    // sensor (variant=measured) + a predicted pump-curve outflow
+    // (variant=predicted) is the common realistic mix.
+    const inflowPick  = this._pickFlowSum(this.flowPositions.inflow,  flowUnit);
+    const outflowPick = this._pickFlowSum(this.flowPositions.outflow, flowUnit);
+    const inflow      = inflowPick.sum;
+    const outflowReal = outflowPick.sum;
 
     if (!this._predictedFlowState) this._predictedFlowState = { inflow, outflow: outflowReal, lastTimestamp: now };