feat(ui): configure maxParallelToolCalls for factory-created agents

The acp and stdio-agent plugins only forwarded `model` into their created
agents, so every factory/ACP deployment was pinned to the agent-loop default
parallel cap with no cordis.yml override. Add a `maxParallelToolCalls` config
field (positive-integer validated) to both, threaded through the existing
per-agent options path — symmetric with `model`.

packages/ui/acp/tests/stream-update.spec.ts

@@ -818,5 +818,7 @@ describe('agentOptions', () => {
   it('includes only the fields present in config', () => {
     expect(agentOptions({})).toEqual({})
     expect(agentOptions({ model: 'm' })).toEqual({ model: 'm' })
+    expect(agentOptions({ maxParallelToolCalls: 3 })).toEqual({ maxParallelToolCalls: 3 })
+    expect(agentOptions({ model: 'm', maxParallelToolCalls: 1 })).toEqual({ model: 'm', maxParallelToolCalls: 1 })
   })
 })