fix: rename _calcTimeRemaining to _calcRemainingTime + add tests

Fix method name mismatch in tick() that called non-existent _calcTimeRemaining
instead of _calcRemainingTime. Add 27 unit tests for specificClass.

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

src/specificClass.js

@@ -211,7 +211,7 @@ class pumpingStation {
     this._updateVolumePrediction("in"); // check for changes in incomming flow
         //calc the most important values back to determine state and net up or downstream flow
     this._calcNetFlow();
-    this._calcTimeRemaining();
+    this._calcRemainingTime();
     
   }