feat(diffuser): resolve supplier curves via assetResolver + wire asset menu

_loadSpecs() now calls loadCurve(model) instead of returning a hardcoded
literal. Default model 'gva-elastox-r' keeps the legacy GVA numbers; the
editor cascade (supplier → type → model → unit) lets users pick Jäger,
Aerostrip, or PIK/PRK once those curve files land in generalFunctions.

Editor changes:
- diffuser.js serves /diffuser/menu.js + /diffuser/configData.js
- diffuser.html loads the shared MenuManager scripts, includes
  asset-fields-placeholder + logger-fields-placeholder, and runs the
  shared init/save lifecycle.
- Density field re-labelled "Bottom coverage [%]" — semantics were
  always meant to be % surface-area coverage; "elements per m²" was a
  prior mis-conversion. Default flipped 2.4 → 15 (typical fine-bubble).
- New defaults: model, unit, assetTagNumber.

specificClass:
- buildDomainConfig now forwards uiConfig.model/unit/assetTagNumber
  under config.asset.* so _loadSpecs can resolve it.
- _loadSpecs walks config.asset.model || config.model || DEFAULT, falls
  through to GVA on a missing curve file (with a clear error if neither
  resolves to a usable otr_curve + p_curve).

All 8 unit + structure tests pass.

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

diffuser.js

@@ -1,9 +1,31 @@
 const nameOfNode = 'diffuser';
 const nodeClass = require('./src/nodeClass.js');
+const { MenuManager, configManager } = require('generalFunctions');
 
 module.exports = function(RED) {
   RED.nodes.registerType(nameOfNode, function(config) {
     RED.nodes.createNode(this, config);
     this.nodeClass = new nodeClass(config, RED, this, nameOfNode);
   });
+
+  const menuMgr = new MenuManager();
+  const cfgMgr  = new configManager();
+
+  RED.httpAdmin.get(`/${nameOfNode}/menu.js`, (req, res) => {
+    try {
+      const script = menuMgr.createEndpoint(nameOfNode, ['asset', 'logger']);
+      res.type('application/javascript').send(script);
+    } catch (err) {
+      res.status(500).send(`// Error generating menu: ${err.message}`);
+    }
+  });
+
+  RED.httpAdmin.get(`/${nameOfNode}/configData.js`, (req, res) => {
+    try {
+      const script = cfgMgr.createEndpoint(nameOfNode);
+      res.type('application/javascript').send(script);
+    } catch (err) {
+      res.status(500).send(`// Error generating configData: ${err.message}`);
+    }
+  });
 };