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>

src/specificClass.js

@@ -359,6 +359,39 @@ class MachineGroup extends BaseDomain {
         return this._demandDispatcher.fireAndWait({ source, demand, powerCap, priorityList });
     }
 
+    // Operator-style entry point: accepts a (value, unit) pair and resolves
+    // to canonical m³/s before delegating to handleInput. Single source of
+    // truth for the unit math shared by the set.demand command handler and
+    // by parent nodes (e.g. pumpingStation level-based control) that hold a
+    // direct reference to this specificClass and need to push a % demand
+    // without re-implementing the interpolation. Negative value is the
+    // stop-all signal regardless of unit.
+    async setDemand(value, unit = '%') {
+        const v = Number(value);
+        if (!Number.isFinite(v)) {
+            this.logger?.error?.(`setDemand: invalid value '${value}'`);
+            return undefined;
+        }
+        if (v < 0) {
+            await this.turnOffAllMachines();
+            return undefined;
+        }
+        let canonical;
+        if (unit === '%') {
+            const dt = this.calcDynamicTotals();
+            canonical = this.interpolation.interpolate_lin_single_point(
+                v, 0, 100, dt.flow.min, dt.flow.max);
+        } else {
+            try {
+                canonical = convert(v).from(unit).to('m3/s');
+            } catch (err) {
+                this.logger?.error?.(`setDemand: cannot convert ${v} ${unit} -> m3/s: ${err?.message || err}`);
+                return undefined;
+            }
+        }
+        return this.handleInput('parent', canonical);
+    }
+
     async _runDispatch(source, demand, powerCap, priorityList) {
         const demandQ = parseFloat(demand);
         if (!Number.isFinite(demandQ)) {