B3.1 + B3.2 + B3.3: ChildRouter fan-out + commandRegistry 'none' + UnitPolicy dual-shape

B3.1 ChildRouter per-listener fan-out (drop emit monkey-patch):
  Partial-filter subscriptions enumerate every concrete
  <type>.measured.<position> event name (cartesian product over
  the canonical POSITIONS list + 19 KNOWN_TYPES) and register a
  plain emitter.on() per combo. Multi-parent semantics are trivial:
  each ChildRouter's listeners are independent. Drop the wrap/unwrap
  bookkeeping in tearDown. ChildRouter.js 184→164 lines.

B3.2 commandRegistry 'none' + description:
  Add 'none' to payloadSchema.type — handler still fires; logs warn
  if msg.payload is non-empty (catches accidental passes). Add
  optional `description` field per descriptor; surfaced via .list()
  so wikiGen can render per-topic effect text.
  commandRegistry.js 157→164 lines. 23/23 tests pass.

B3.3 UnitPolicy dual-shape:
  policy.canonical/output/curve are now BOTH callable methods AND
  frozen property bags. policy.canonical('flow') === 'm3/s' and
  policy.canonical.flow === 'm3/s' both work. Property bags are
  frozen (assign/delete/redefine throw in strict). Drops the
  _unitView workaround in MGC + rotatingMachine specificClass.
  UnitPolicy.js 149→163 lines, 15/15 tests pass.

CONTRACTS.md §4 + §6 updated.

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

test/basic/commandRegistry.basic.test.js

@@ -151,15 +151,62 @@ test('list() returns descriptors without handler functions', () => {
         topic: 'set.mode',
         aliases: ['setMode'],
         payloadSchema: { type: 'string' },
+        description: null,
     });
     assert.deepEqual(list[1], {
         topic: 'cmd.startup',
         aliases: [],
         payloadSchema: null,
+        description: null,
     });
     for (const d of list) assert.ok(!('handler' in d), 'handler must not be in descriptor');
 });
 
+test("payloadSchema type 'none' invokes handler with no payload and no warning", async () => {
+    const logger = makeLogger();
+    let invoked = 0;
+    const reg = createRegistry([{
+        topic: 'cmd.calibrate',
+        payloadSchema: { type: 'none' },
+        handler: () => { invoked += 1; },
+    }], { logger });
+
+    await reg.dispatch({ topic: 'cmd.calibrate' }, {}, {});
+    await reg.dispatch({ topic: 'cmd.calibrate', payload: undefined }, {}, {});
+    await reg.dispatch({ topic: 'cmd.calibrate', payload: null }, {}, {});
+    assert.equal(invoked, 3);
+    assert.equal(logger._calls.warn.length, 0);
+});
+
+test("payloadSchema type 'none' invokes handler with non-empty payload but logs warn", async () => {
+    const logger = makeLogger();
+    let invoked = 0;
+    const reg = createRegistry([{
+        topic: 'cmd.calibrate',
+        payloadSchema: { type: 'none' },
+        handler: () => { invoked += 1; },
+    }], { logger });
+
+    await reg.dispatch({ topic: 'cmd.calibrate', payload: 'ignored' }, {}, {});
+    await reg.dispatch({ topic: 'cmd.calibrate', payload: { a: 1 } }, {}, {});
+    await reg.dispatch({ topic: 'cmd.calibrate', payload: 0 }, {}, {});
+    assert.equal(invoked, 3);
+    const warns = logger._calls.warn.filter((m) => m.includes('payload ignored'));
+    assert.equal(warns.length, 3);
+    assert.ok(warns[0].includes('cmd.calibrate'));
+    assert.ok(warns[0].includes('trigger-only'));
+});
+
+test('list() includes description field when present', () => {
+    const reg = createRegistry([
+        { topic: 'cmd.calibrate', payloadSchema: { type: 'none' }, description: 'Trigger calibration.', handler: () => {} },
+        { topic: 'set.mode', payloadSchema: { type: 'string' }, handler: () => {} },
+    ]);
+    const list = reg.list();
+    assert.equal(list[0].description, 'Trigger calibration.');
+    assert.equal(list[1].description, null);
+});
+
 test('deprecationStats reflects alias hit counts', async () => {
     const logger = makeLogger();
     const reg = createRegistry([{