Hold-then-ramp shift semantics + shiftArmPercent + e2e tests

Runtime (specificClass.js):
- Replace the "shift left both ramp ends" geometry with a true
  hold-then-ramp hysteresis driven by output %, not level:
  • Up-curve % crosses shiftArmPercent on the way up → ARM.
  • Filling→draining transition while armed → capture the up-curve %
    at that moment as _shiftHoldValue.
  • Draining + level ≥ shiftLevel → output stays at _shiftHoldValue
    (horizontal hold, matching the dashed segment in the SVG).
  • Draining + level in [start, shift] → output ramps holdValue → 0 %
    along the same curve shape (linear or log) as the up curve.
  • Draining + level < startLevel → 0 % AND disarm.
  • Returning to filling clears holdValue, stays armed; next drain
    transition captures a fresh hold so bouncing fills rearm cleanly.
  • Disarm only when level ≤ startLevel.
- New _curveShape(x) helper for shared linear/log shaping.
- Removed legacy _levelBasedRampStart / _levelBasedRampTop /
  _updateShiftArmed in favour of the inline state machine.

Adapter (nodeClass.js):
- Pipe shiftArmPercent through to control.levelbased.

Editor (pumpingStation.html + src/editor/):
- Add shiftArmPercent input row (% with unit) to the mode side panel
  (only shown when shifted ramp is enabled). Default 95 %.
- Add the horizontal arming-% line + label inside the mode SVG —
  this is the "% Threshold triggering shifted ramp down" line from
  the original drawing that had been missing.
- Redraw the shifted-down curve to match the SVG geometry literally:
  100 % flat from maxLevel → shiftLevel, then ramp shiftLevel →
  startLevel down to 0 %, OFF below startLevel. Preview shows the
  worst-case envelope (hold = 100 %); runtime hold is captured live.
- Validation extended: 0 < shiftArmPercent ≤ 100; ordering rules
  preserved (start < shift ≤ max etc.).
- Auto-default shiftArmPercent to 95 when shift is enabled and the
  current value is missing or out of range.

Dashboard example (examples/basic-dashboard.flow.json):
- Parser now reads `level.predicted.atequipment.default` etc. The
  MeasurementContainer flatten format includes the implicit 'default'
  childId; consumers must include it. Comment in the parser points
  at the documenting source in generalFunctions.

Tests:
- test/basic: replace old level-armed-shift tests with two new ones
  that exercise the hold-then-ramp arming, capture, hold, ramp-down,
  disarm, and the bounce case (filling→draining→filling→draining
  captures a fresh hold each time).
- test/integration/shifted-ramp-end-to-end.test.js: new file. Drives
  Q_IN/Q_OUT through the full runtime tick with a controllable clock,
  asserting the same hysteresis path the dashboard exercises.
- test/integration/basic-dashboard-flow.test.js: fixture keys updated
  to the .default-suffixed form so they match the real flatten output.
56/56 tests pass.

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

pumpingStation.html

@@ -83,6 +83,7 @@
       logCurveFactor: { value: 9 },
       enableShiftedRamp: { value: false },
       shiftLevel: { value: 0 },
+      shiftArmPercent: { value: 95 },
       startLevel: { value: null },
       minLevel: { value: null },
       maxLevel: { value: null },
@@ -417,10 +418,15 @@
         <span class="ps-unit">m</span>
       </div>
       <div class="ps-row" id="ps-shiftLevel-row" data-stroke="#D68910" data-couples-line="ps-mode-line-shiftLevel" style="display:none;">
-        <div><label>shiftLevel</label><div class="ps-sub">arms hysteresis</div></div>
+        <div><label>shiftLevel</label><div class="ps-sub">held output drops here</div></div>
         <input type="number" id="node-input-shiftLevel" min="0" step="0.01" />
         <span class="ps-unit">m</span>
       </div>
+      <div class="ps-row" id="ps-shiftArmPercent-row" data-stroke="#D68910" data-couples-line="ps-mode-line-armPercent" style="display:none;">
+        <div><label>shiftArmPercent</label><div class="ps-sub">arms when output % crosses this</div></div>
+        <input type="number" id="node-input-shiftArmPercent" min="0" max="100" step="1" />
+        <span class="ps-unit">%</span>
+      </div>
       <div class="ps-row ps-readonly" data-stroke="#C0392B" data-couples-line="ps-mode-line-overflowLevel">
         <div><label>overflowLevel</label><div class="ps-sub">from basin above</div></div>
         <span id="ps-mode-readout-overflow" class="ps-readonly-val">— m</span>
@@ -461,6 +467,10 @@
       <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" />
       <line id="ps-mode-line-shiftLevel" y1="24" y2="140" stroke="#D68910" stroke-dasharray="2 2" style="display:none;" />
+      <!-- Horizontal arming-% line — y is set DYNAMICALLY by the JS to the
+           shiftArmPercent value (in plot-y space). Spans full plot width. -->
+      <line id="ps-mode-line-armPercent" x1="52" x2="402" stroke="#D68910" stroke-dasharray="4 3" stroke-width="1" opacity="0.7" style="display:none;" />
+      <text id="ps-mode-label-armPercent" x="404" text-anchor="start" fill="#D68910" font-size="9" style="display:none;">arm%</text>
       <!-- Axis labels — y=180 row sits below the OFF baseline (y=160). x set dynamically. -->
       <text id="ps-mode-label-dryRunLevel"  y="180" text-anchor="middle" fill="#C0392B">dry run</text>
       <text id="ps-mode-label-startLevel" y="180" text-anchor="middle" fill="#1E8449">start</text>
@@ -472,7 +482,7 @@
            so they never collide with the title (y=14). Up-caption left-aligned at
            x=60; down-caption to its right at x=210. Both font-size 10. -->
       <text id="ps-mode-curve-up-label" x="60" y="205" fill="#1E8449" font-size="10">— ramp inlet→max</text>
-      <text id="ps-mode-curve-down-label" x="210" y="205" fill="#D68910" font-size="10" style="display:none;">— shifted start→shift</text>
+      <text id="ps-mode-curve-down-label" x="210" y="205" fill="#D68910" font-size="10" style="display:none;">— shifted (held @100% then ramp shift→start)</text>
     </svg>
     </div>
   </div>