Output manager ignores requested port ID

### Feature Summary

`OutputManager.get_port` ignores an explicit port ID and always returns the first output port. A worker with multiple output ports can therefore receive the wrong schema when it requests a nonfirst port. Unknown IDs are also silently treated as the first port.

Expected behavior: an explicit port ID returns that port and an unknown ID fails clearly.

Before: requesting port 1 returns port 0

After: requesting port 1 returns port 1

Reproduction evidence:

Add two output ports with distinct schemas, then call `get_port` with the second port ID. The returned worker port contains the first schema.

Version and commit evidence:

1.3.0-incubating-SNAPSHOT on main

**Commit Hash (Optional)**
50321e403c82df299a13deb50a7f9849dd93bdba

**Browsers**

Not browser specific

**Relevant log output**

Requested port 1 but received the schema registered for port 0.

### Proposed Solution or Design

Expected behavior: an explicit port ID returns that port and an unknown ID fails clearly.

After: requesting port 1 returns port 1

### Affected Area

Workflow Engine (Amber)