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>

pumpingStation.html

@@ -86,6 +86,8 @@
       shiftArmPercent: { value: 95 },
       startLevel: { value: 1 },     // m, pump-on threshold (engagement edge)
       stopLevel: { value: 0.5 },    // m, pump-off threshold (hysteresis fall-back)
+      holdLevel: { value: 1 },      // m, ramp 0%-foot; defaults to startLevel (= no hold zone)
+      deadZoneKeepAlivePercent: { value: 1 }, // % emitted across [stopLevel, startLevel] keep-alive band
       minLevel: { value: 0.3 },     // m, hard-stop (just above outflow pipe top)
       maxLevel: { value: 3.8 },     // m, 100% demand saturation
       flowSetpoint: { value: null },
@@ -418,6 +420,11 @@
         <input type="number" id="node-input-stopLevel" min="0" step="0.01" />
         <span class="ps-unit">m</span>
       </div>
+      <div class="ps-row" data-stroke="#27AE60" data-couples-line="ps-mode-line-holdLevel">
+        <div><label>holdLevel</label><div class="ps-sub">0 % ramp foot — leave at startLevel for no hold band</div></div>
+        <input type="number" id="node-input-holdLevel" min="0" step="0.01" />
+        <span class="ps-unit">m</span>
+      </div>
       <div class="ps-row ps-readonly" data-stroke="#1F4E79" data-couples-line="ps-mode-line-inflowLevel">
         <div><label>inflowLevel</label><div class="ps-sub">from basin above</div></div>
         <span id="ps-mode-readout-inflow" class="ps-readonly-val">— m</span>
@@ -475,6 +482,7 @@
       <line id="ps-mode-line-dryRunLevel"  y1="24" y2="140" stroke="#C0392B" stroke-dasharray="2 2" />
       <line id="ps-mode-line-startLevel" y1="24" y2="140" stroke="#1E8449" stroke-dasharray="2 2" />
       <line id="ps-mode-line-stopLevel" y1="24" y2="140" stroke="#7D3C98" stroke-dasharray="2 2" />
+      <line id="ps-mode-line-holdLevel" y1="24" y2="140" stroke="#27AE60" stroke-dasharray="2 2" />
       <line id="ps-mode-line-inflowLevel" y1="24" y2="140" stroke="#1F4E79" stroke-dasharray="2 2" />
       <line id="ps-mode-line-maxLevel" y1="24" y2="140" stroke="#D68910" stroke-dasharray="2 2" />
       <line id="ps-mode-line-overflowLevel" y1="24" y2="140" stroke="#C0392B" stroke-dasharray="2 2" />