bus: tester identity for PM tests (row 110, #1604)

A tester binds with a process proof from the bus's own tester-cli.mjs
when the business var bus.tester is true. It may send [mos test] messages
to a role, receive replies on the tester address and use the read verbs;
every other verb refuses. Messages store from_role tester and write no
human.input event. turnRequest() marks them as never Jason's instruction.
human.mjs is unchanged.

Candidate manifest bdaf7f476abd0b2b5095ab2f7f43e38540e6ba48ee14a02a4f4995a1469b79df
(Darkwing round 2, packet 9f1563ec1), BASE badfa52b9. Approved by Filbert
(comment 28360) and Sage (comment 28361). Sage gate rerun passed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/bus/src/runtime.mjs

@@ -5,6 +5,7 @@ import { Broker, BusError } from './broker.mjs';
 import { Credentials } from './credentials.mjs';
 import { serve } from './server.mjs';
 import { verifyHuman } from './human.mjs';
+import { verifyTester } from './tester.mjs';
 // Trusted host API. S1 supplies resolved definitions, S6 supplies launch records and ends them.
 // Neither a business-file writer nor a socket-accessible configuration endpoint.
 // `tasks` is S3's adapter factory: ({broker, credentials, businesses}) => {handle, timeout, close}.
@@ -72,6 +73,15 @@ export async function startBroker({
         if (!human) throw new BusError('unknown-business');
         return broker.bindHuman({ business, human, via: 'cli', outsideAgent: true });
       },
+      // Row 110 (#1604): a tester proves its CLI process and that no managed run is above it.
+      // The broker then binds only if the business sets `bus.tester` to true.
+      authenticateTester: (proof) => {
+        const { business } = verifyTester(proof, {
+          cliPath: fileURLToPath(new URL('./tester-cli.mjs', import.meta.url)),
+          launches: launchRecords,
+        });
+        return broker.bindTester({ business });
+      },
     });
     // S6 launcher operations. The host decides capacity and the instance list; the broker
     // authorizes role.launch and keeps the evidence, refusals included.