[feature]: Add neuralwatt subscription support

[bekriebel]

Pre-flight checks

• I searched existing issues and did not find a duplicate request.
• I reviewed current behavior on the production released OpenCode version.

OpenCode version reviewed

1.17.11

Problem statement

Neuralwatt quotas are not currently supported

Proposed change

Add the subscriptions from neuralwatt.com to opencode-quota. Having it show overages and pay-as-you-go metrics would be ideal.

Alternatives considered

No response

Acceptance criteria

• Neuralwatt subscription information acquired and shown
• Neuralwatt credits remaining information acquired and shown

[bekriebel]

I'll attempt a quick PR for this.