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>

examples/basic-dashboard.flow.json

@@ -295,7 +295,7 @@
     "type": "function",
     "z": "ps_tab_basic_dashboard",
     "name": "Parse PS output",
-    "func": "const fields = (msg.payload && typeof msg.payload === 'object') ? msg.payload : {};\nconst snapshot = Object.assign({}, context.get('snapshot') || {}, fields);\ncontext.set('snapshot', snapshot);\nconst firstFinite = (...keys) => {\n  for (const key of keys) {\n    const value = Number(snapshot[key]);\n    if (Number.isFinite(value)) return value;\n  }\n  return null;\n};\nconst level = firstFinite('level.predicted.atequipment', 'level.measured.atequipment');\nconst volume = firstFinite('volume.predicted.atequipment', 'volume.measured.atequipment');\nconst netFlow = firstFinite('netFlowRate.predicted.atequipment', 'netFlowRate.measured.atequipment');\nconst demand = firstFinite('percControl');\nconst safety = snapshot.safetyState || 'normal';\nconst direction = snapshot.direction || 'unknown';\nconst overflow = snapshot.isOverflowing === true || snapshot.isOverflowing === 'true';\nconst timeleft = Number(snapshot.timeleft);\nconst fmt = (value, digits = 2) => Number.isFinite(value) ? value.toFixed(digits) : '-';\nreturn [\n  level == null ? null : { topic: 'level', payload: level },\n  volume == null ? null : { topic: 'volume', payload: volume },\n  demand == null ? null : { topic: 'demand', payload: demand },\n  netFlow == null ? null : { topic: 'net_flow', payload: netFlow },\n  { topic: 'safety', payload: `${safety} | overflowing=${overflow}` },\n  { topic: 'snapshot', payload: `level=${fmt(level)} m | volume=${fmt(volume)} m3 | demand=${fmt(demand, 0)}% | direction=${direction} | t=${Number.isFinite(timeleft) ? Math.round(timeleft) + ' s' : '-'}` }\n];",
+    "func": "// MeasurementContainer flat keys are `${type}.${variant}.${position}.${childId}`.\n// When PS writes without an explicit .child(), the childId is the literal\n// string 'default' — DON'T strip it. See generalFunctions/src/measurements/\n// MeasurementContainer.js getFlattenedOutput for details.\nconst fields = (msg.payload && typeof msg.payload === 'object') ? msg.payload : {};\nconst snapshot = Object.assign({}, context.get('snapshot') || {}, fields);\ncontext.set('snapshot', snapshot);\nconst firstFinite = (...keys) => {\n  for (const key of keys) {\n    const value = Number(snapshot[key]);\n    if (Number.isFinite(value)) return value;\n  }\n  return null;\n};\nconst level = firstFinite('level.predicted.atequipment.default', 'level.measured.atequipment.default');\nconst volume = firstFinite('volume.predicted.atequipment.default', 'volume.measured.atequipment.default');\nconst netFlow = firstFinite('netFlowRate.predicted.atequipment.default', 'netFlowRate.measured.atequipment.default');\nconst demand = firstFinite('percControl');\nconst safety = snapshot.safetyState || 'normal';\nconst direction = snapshot.direction || 'unknown';\nconst overflow = snapshot.isOverflowing === true || snapshot.isOverflowing === 'true';\nconst timeleft = Number(snapshot.timeleft);\nconst fmt = (value, digits = 2) => Number.isFinite(value) ? value.toFixed(digits) : '-';\nreturn [\n  level == null ? null : { topic: 'level', payload: level },\n  volume == null ? null : { topic: 'volume', payload: volume },\n  demand == null ? null : { topic: 'demand', payload: demand },\n  netFlow == null ? null : { topic: 'net_flow', payload: netFlow },\n  { topic: 'safety', payload: `${safety} | overflowing=${overflow}` },\n  { topic: 'snapshot', payload: `level=${fmt(level)} m | volume=${fmt(volume)} m3 | demand=${fmt(demand, 0)}% | direction=${direction} | t=${Number.isFinite(timeleft) ? Math.round(timeleft) + ' s' : '-'}` }\n];",
     "outputs": 6,
     "noerr": 0,
     "initialize": "",