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/editor/oneditprepare.js

@@ -65,6 +65,14 @@
 
     // Numeric field defaults.
     ns.setNumberField('node-input-startLevel',     node.startLevel);
+    ns.setNumberField('node-input-stopLevel',      node.stopLevel);
+    // holdLevel defaults to startLevel when omitted (no hold band). Show
+    // the saved value if there is one; otherwise mirror startLevel so the
+    // user immediately sees the "no hold band" baseline.
+    ns.setNumberField('node-input-holdLevel',
+      Number.isFinite(node.holdLevel) ? node.holdLevel : node.startLevel);
+    ns.setNumberField('node-input-deadZoneKeepAlivePercent',
+      Number.isFinite(node.deadZoneKeepAlivePercent) ? node.deadZoneKeepAlivePercent : 1);
     ns.setNumberField('node-input-maxLevel',       node.maxLevel);
     ns.setNumberField('node-input-logCurveFactor', node.logCurveFactor);
     ns.setNumberField('node-input-shiftLevel',     node.shiftLevel);
@@ -77,16 +85,22 @@
     const shiftCheckbox = document.getElementById('node-input-enableShiftedRamp');
     if (shiftCheckbox) shiftCheckbox.checked = !!node.enableShiftedRamp;
 
-    // Bind redraws to the inputs each diagram cares about.
+    // Bind redraws to the inputs each diagram cares about. The basin
+    // diagram itself only paints inflow/outflow/overflow lines, but its
+    // validation ribbon also enforces startLevel/holdLevel/maxLevel
+    // ordering — so it has to refire when any of those change too, or
+    // the "Fix before deploy" ribbon goes stale mid-edit.
     ns.bindRedraw(
       ['basinHeight', 'overflowLevel', 'inflowLevel', 'outflowLevel',
+       'startLevel', 'stopLevel', 'holdLevel', 'maxLevel',
        'dryRunThresholdPercent', 'highVolumeSafetyThresholdPercent'],
       ns.basinDiagram.redraw
     );
     ns.bindRedraw(
       // dryRunLevel is derived (outflowLevel + dryRunThresholdPercent),
       // so the mode preview must redraw when either of those change.
-      ['startLevel', 'maxLevel', 'inflowLevel', 'outflowLevel', 'overflowLevel',
+      ['startLevel', 'stopLevel', 'holdLevel', 'maxLevel',
+       'inflowLevel', 'outflowLevel', 'overflowLevel',
        'dryRunThresholdPercent',
        'levelCurveType', 'logCurveFactor', 'enableShiftedRamp', 'shiftLevel',
        'shiftArmPercent'],
@@ -97,7 +111,7 @@
     // so the next redraw + validation sees the correct min/max attrs.
     ns.bindRedraw(
       ['basinHeight', 'basinVolume', 'overflowLevel', 'maxLevel',
-       'inflowLevel', 'startLevel', 'outflowLevel',
+       'inflowLevel', 'startLevel', 'stopLevel', 'holdLevel', 'outflowLevel',
        'dryRunThresholdPercent', 'highVolumeSafetyThresholdPercent',
        'enableShiftedRamp', 'shiftLevel', 'shiftArmPercent'],
       () => ns.bounds?.apply()