feat: add node tests, integration tests, API reference, fix pumpingStation bug

- Add 127 unit tests for measurement, pumpingStation, reactor, settler specificClass
- Add 32 integration tests for parent-child registration flows
- Fix pumpingStation tick() calling non-existent _calcTimeRemaining (was _calcRemainingTime)
- Add API reference documentation for all generalFunctions modules

Total tests: 536 (389 Jest + 23 node:test + 124 legacy), all passing

Closes #17, #19, #20

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

jest.config.js

@@ -4,6 +4,10 @@ module.exports = {
   testMatch: [
     '<rootDir>/nodes/generalFunctions/src/coolprop-node/test/**/*.test.js',
     '<rootDir>/nodes/generalFunctions/test/**/*.test.js',
+    '<rootDir>/nodes/pumpingStation/test/**/*.test.js',
+    '<rootDir>/nodes/reactor/test/**/*.test.js',
+    '<rootDir>/nodes/settler/test/**/*.test.js',
+    '<rootDir>/nodes/measurement/test/**/*.test.js',
   ],
   testPathIgnorePatterns: [
     '/node_modules/',