feat: digital (MQTT) mode + fix silent dispatcher bug for camelCase methods

Runtime:
- Fix silent no-op when user selected any camelCase smoothing or outlier
  method from the editor. validateEnum in generalFunctions lowercases enum
  values (zScore -> zscore, lowPass -> lowpass, ...) but the dispatcher
  compared against camelCase keys. Effect: 5 of 11 smoothing methods
  (lowPass, highPass, weightedMovingAverage, bandPass, savitzkyGolay) and
  2 of 3 outlier methods (zScore, modifiedZScore) silently fell through.
  Users got the raw last value or no outlier filtering with no error log.
  Review any pre-2026-04-13 flows that relied on these methods.
  Fix: normalize method names to lowercase on both sides of the lookup.

- New Channel class (src/channel.js) — self-contained per-channel pipeline:
  outlier -> offset -> scaling -> smoothing -> min/max -> constrain -> emit.
  Pure domain logic, no Node-RED deps, reusable by future nodes that need
  the same signal-conditioning chain.

Digital mode:
- config.mode.current = 'digital' opts in. config.channels declares one
  entry per expected JSON key; each channel has its own type, position,
  unit, distance, and optional scaling/smoothing/outlierDetection blocks
  that override the top-level analog-mode fields. One MQTT-shaped payload
  ({t:22.5, h:45, p:1013}) dispatches N independent pipelines and emits N
  MeasurementContainer slots from a single input message.
- Backward compatible: absent mode config = analog = pre-digital behaviour.
  Every existing measurement flow keeps working unchanged.

UI:
- HTML editor: new Mode dropdown and Channels JSON textarea. The Node-RED
  help panel is rewritten end-to-end with topic reference, port contracts,
  per-mode configuration, smoothing/outlier method tables, and a note
  about the pre-fix behaviour.
- README.md rewritten (was a one-line stub).

Tests (12 -> 71, all green):
- test/basic/smoothing-methods.basic.test.js (+16): every smoothing method
  including the formerly-broken camelCase ones.
- test/basic/outlier-detection.basic.test.js (+10): every outlier method,
  fall-through, toggle.
- test/basic/scaling-and-interpolation.basic.test.js (+10): offset,
  interpolateLinear, constrain, handleScaling edge cases, min/max
  tracking, updateOutputPercent fallback, updateOutputAbs emit dedup.
- test/basic/calibration-and-stability.basic.test.js (+11): calibrate
  (stable and unstable), isStable, evaluateRepeatability refusals,
  toggleSimulation, tick simulation on/off.
- test/integration/digital-mode.integration.test.js (+12): channel build
  (including malformed entries), payload dispatch, multi-channel emit,
  unknown keys, per-channel scaling/smoothing/outlier, empty channels,
  non-numeric value rejection, getDigitalOutput shape, analog-default
  back-compat.

E2E verified on Dockerized Node-RED: analog regression unchanged; digital
mode deploys with three channels, dispatches MQTT-style payload, emits
per-channel events, accumulates per-channel smoothing, ignores unknown
keys.

Depends on generalFunctions commit e50be2e (permissive unit check +
mode/channels schema).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

measurement.html

@@ -20,7 +20,11 @@
       // Define default properties
       name: { value: "" }, // use asset category as name
 
-      // Define specific properties
+      // Input mode: 'analog' (scalar payload, default) or 'digital' (object payload, many channels)
+      mode: { value: "analog" },
+      channels: { value: "[]" },
+
+      // Define specific properties (analog-mode pipeline defaults)
       scaling: { value: false },
       i_min: { value: 0, required: true },
       i_max: { value: 0, required: true },
@@ -141,7 +145,7 @@
       }
 
       // Save basic properties
-      ["smooth_method"].forEach(
+      ["smooth_method", "mode", "channels"].forEach(
         (field) => (node[field] = document.getElementById(`node-input-${field}`).value || "")
       );
 
@@ -167,6 +171,23 @@
 
 <script type="text/html" data-template-name="measurement">
 
+  <!-- Input mode -->
+  <div class="form-row">
+    <label for="node-input-mode"><i class="fa fa-exchange"></i> Input Mode</label>
+    <select id="node-input-mode" style="width:60%;">
+      <option value="analog">analog — one scalar per msg.payload (classic PLC)</option>
+      <option value="digital">digital — object payload with many channel keys (MQTT/IoT)</option>
+    </select>
+  </div>
+
+  <div class="form-row" id="row-input-channels">
+    <label for="node-input-channels"><i class="fa fa-list"></i> Channels (JSON)</label>
+    <textarea id="node-input-channels" rows="6" style="width:60%; font-family:monospace;" placeholder='[{"key":"temperature","type":"temperature","position":"atEquipment","unit":"C","scaling":{"enabled":false,"inputMin":0,"inputMax":1,"absMin":-50,"absMax":150,"offset":0},"smoothing":{"smoothWindow":5,"smoothMethod":"mean"}}]'></textarea>
+    <div class="form-tips">Digital mode only. One entry per payload key. See README for schema.</div>
+  </div>
+
+  <hr>
+
   <!-- Scaling Checkbox -->
   <div class="form-row">
     <label for="node-input-scaling"
@@ -256,20 +277,49 @@
 
 
 <script type="text/html" data-help-name="measurement">
-  <p><b>Measurement Node</b>: Scales, smooths, and simulates measurement data.</p>
-  <p>Use this node to scale, smooth, and simulate measurement data. The node can be configured to scale input data to a specified range, smooth the data using a variety of methods, and simulate data for testing purposes.</p>
-  <li><b>Supplier:</b> Select a supplier to populate machine options.</li>
-  <li><b>SubType:</b> Select a subtype if applicable to further categorize the asset.</li>
-  <li><b>Model:</b> Define the specific model for more granular asset configuration.</li>
-  <li><b>Unit:</b> Assign a unit to standardize measurements or operations.</li>
-  <li><b>Scaling:</b> Enable or disable input scaling. When enabled, you must provide the source min and max values.</li>
-  <li><b>Source Min/Max:</b> Define the minimum and maximum values for the input range when scaling is enabled.</li>
-  <li><b>Input Offset:</b> Specify an offset value to be added to the input measurement.</li>
-  <li><b>Process Min/Max:</b> Define the minimum and maximum values for the output range after processing.</li>
-  <li><b>Simulator:</b> Activate internal simulation for testing purposes.</li>
-  <li><b>Smoothing:</b> Select a smoothing method to apply to the measurement data.</li>
-  <li><b>Window:</b> Define the number of samples to use for smoothing.</li>
-  <li><b>Enable Log:</b> Enable or disable logging for this node.</li>
-  <li><b>Log Level:</b> Select the log level (Info, Debug, Warn, Error) for logging messages.</li>
+  <p><b>Measurement</b>: signal conditioning for a sensor or a bundle of sensors. Runs offset → scaling → smoothing → outlier filtering on each incoming value and publishes into the shared <code>MeasurementContainer</code>.</p>
 
+  <h3>Input modes</h3>
+  <ul>
+    <li><b>analog</b> (default) — <code>msg.payload</code> is a single number (PLC / 4-20 mA style). One pipeline, one output measurement.</li>
+    <li><b>digital</b> — <code>msg.payload</code> is an object with many keys (MQTT / JSON IoT). Each key maps to its own <i>channel</i> with independent scaling, smoothing, outlier detection, type, position, unit. One message → N measurements.</li>
+  </ul>
+
+  <h3>Topics (<code>msg.topic</code>)</h3>
+  <ul>
+    <li><code>measurement</code> — main input. analog: number; digital: object keyed by channel names.</li>
+    <li><code>simulator</code> — toggle the internal random-walk source.</li>
+    <li><code>outlierDetection</code> — toggle the outlier filter.</li>
+    <li><code>calibrate</code> — set offset so current output matches <code>Source Min</code> (scaling on) / <code>Process Min</code> (scaling off). Requires a stable window.</li>
+  </ul>
+
+  <h3>Output ports</h3>
+  <ol>
+    <li><b>process</b> — delta-compressed payload. analog: <code>{mAbs, mPercent, totalMinValue, totalMaxValue, totalMinSmooth, totalMaxSmooth}</code>. digital: <code>{channels: { key: {...} }}</code>.</li>
+    <li><b>dbase</b> — InfluxDB line-protocol telemetry.</li>
+    <li><b>parent</b> — <code>registerChild</code> handshake for the parent equipment node.</li>
+  </ol>
+
+  <h3>Analog configuration</h3>
+  <ul>
+    <li><b>Scaling</b>: enables linear interpolation from <code>[Source Min, Source Max]</code> to <code>[Process Min, Process Max]</code>.</li>
+    <li><b>Input Offset</b>: additive bias applied before scaling.</li>
+    <li><b>Smoothing</b>: <code>none</code> | <code>mean</code> | <code>min</code> | <code>max</code> | <code>sd</code> | <code>lowPass</code> | <code>highPass</code> | <code>weightedMovingAverage</code> | <code>bandPass</code> | <code>median</code> | <code>kalman</code> | <code>savitzkyGolay</code>.</li>
+    <li><b>Window</b>: sample count for the smoothing window.</li>
+    <li><b>Outlier detection</b> (via <code>outlierDetection</code> topic toggle): <code>zScore</code>, <code>iqr</code>, <code>modifiedZScore</code>.</li>
+  </ul>
+
+  <h3>Digital configuration</h3>
+  <p>Populate the <b>Channels (JSON)</b> field with an array. Each entry:</p>
+  <pre>{
+  "key":      "temperature",
+  "type":     "temperature",
+  "position": "atEquipment",
+  "unit":     "C",
+  "scaling":  { "enabled": false, "inputMin": 0, "inputMax": 1, "absMin": -50, "absMax": 150, "offset": 0 },
+  "smoothing": { "smoothWindow": 5, "smoothMethod": "mean" },
+  "outlierDetection": { "enabled": true, "method": "zScore", "threshold": 3 }
+}</pre>
+  <p><code>scaling</code>, <code>smoothing</code>, <code>outlierDetection</code> are optional — missing sections fall back to the analog-mode fields above.</p>
+  <p>Unknown <code>type</code> values (anything not in <code>pressure/flow/power/temperature/volume/length/mass/energy</code>) are accepted without unit compatibility checks, so user-defined channels like <code>humidity</code>, <code>co2</code>, <code>voc</code> work out of the box.</p>
 </script>