Start a build configuration and forward an agent port to localhost

### Area

Build Operations (run, trigger, cancel, logs)

### Problem or use case

I want to start a build configuration that prepares a remote workspace and runs a service, then connect a local client to it. For example, run a Codex app-server in the TeamCity environment and use the local Codex terminal UI, without manually finding the assigned agent and configuring a tunnel.

### Proposed solution

Illustrative syntax:

```bash
# Terminal 1 (proposed syntax)
teamcity run start Remote_Codex --forward-port 1144:4500

# Terminal 2
codex --remote ws://127.0.0.1:1144
```

Here, the build configuration starts a Codex app-server on port `4500` of its build agent. The proposed flag exposes it locally on `127.0.0.1:1144`.

Expected behavior:

- Start the specified configuration with the usual branch, revision, and parameter options; wait for the run and remote port to become ready.
- Forward TCP traffic to the agent assigned to that run, including agents without direct inbound access from the user's machine.
- Bind to localhost by default, print the run URL and local endpoint, and keep the tunnel open in the foreground.
- Report startup, port-binding, and connection failures; close the tunnel when the run ends and make detach versus build cancellation explicit on interruption.

The forwarding mechanism should work for arbitrary TCP services, including web previews and debuggers.

### Alternatives considered

Start the run, find its agent, and configure SSH port forwarding manually. This requires separate connection setup and direct access to the agent.

### Contribution

- [ ] I'd be willing to submit a PR (once it's `status:finalized`)

Start by tracing the existing build-configuration run flow and agent connectivity; the issue names no files or tests. Define how the command starts a run, waits for the remote port, forwards arbitrary TCP traffic on localhost, reports failures, and handles interruption, completion, detachment, and cancellation.

Written by the indexing model from the issue text.