feat(setDemand): surface specificClass.setDemand(value, unit='%') + slim npm pack

Why:
- pumpingStation level-based control was calling MGC.handleInput(percent)
  directly. handleInput expects canonical m³/s; a 1 % keep-alive arrived
  as 1 m³/s ≈ 3600 m³/h, the dispatcher clamped to dt.flow.max and the
  group ran at 100 %. The unit math already existed inside the set.demand
  command handler — but only that handler could reach it.

What:
- New public method `async setDemand(value, unit='%')` on MachineGroup
  (specificClass.js). Resolves the unit (`%` → interpolate against the
  dynamic-totals envelope, absolute units → convert(value)) and calls
  handleInput with canonical m³/s. Negative value remains the operator
  stop-all signal. Single source of truth for the percent → m³/s rule.
- Refactor handlers.setDemand to parse the payload + apply mode gating
  and then delegate to source.setDemand. Drops the local `convert` import
  (now reached via the source).
- Update commands.basic.test.js mock with a setDemand shim that mirrors
  the real method, so existing handleInput assertions still hold.

Packaging:
- Add .npmignore mirroring .gitignore plus dev-only trees (test/, wiki/,
  CLAUDE.md, …) so the published tarball stays small.
- Extend .gitignore with the standard dev-artifact deny list.

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

test/basic/commands.basic.test.js

@@ -65,9 +65,25 @@ function makeSource({
       if (handleInputResult instanceof Error) throw handleInputResult;
       return handleInputResult;
     },
-    // Used by set.demand handler when unit is %: needs dt.flow + interpolation.
-    // With min=0, max=100, the linear interpolation is identity so a bare
-    // numeric demand round-trips through handleInput unchanged.
+    // Mirror of the real specificClass.setDemand: resolves unit -> canonical
+    // m³/s and forwards to handleInput. With dt.flow {min:0,max:100} the %
+    // interpolation is identity, so a bare numeric demand round-trips through
+    // handleInput unchanged — keeping the existing assertions stable.
+    setDemand: async (value, unit = '%') => {
+      const v = Number(value);
+      if (!Number.isFinite(v)) return undefined;
+      if (v < 0) { await source.turnOffAllMachines(); return undefined; }
+      let canonical;
+      if (unit === '%') {
+        canonical = source.interpolation.interpolate_lin_single_point(
+          v, 0, 100, dt.flow.min, dt.flow.max);
+      } else {
+        const { convert } = require('generalFunctions');
+        canonical = convert(v).from(unit).to('m3/s');
+      }
+      return source.handleInput('parent', canonical);
+    },
+    // Retained for completeness — the mock setDemand uses these internally.
     calcDynamicTotals: () => dt,
     interpolation: {
       interpolate_lin_single_point: (x, ix, iy, ox, oy) => {