fix: disable workspace calls when OPENCLAW_WORKSPACE_URL is unset

[moltar-bot]

Summary

• remove the implicit in-cluster workspace fallback URL from openclawWorkspaceClient
• require explicit OPENCLAW_WORKSPACE_URL in all environments
• return SERVICE_NOT_CONFIGURED immediately when URL is missing (no retries/no network calls)
• add unit tests covering missing URL behavior in production and configured URL usage

Why

Without an explicit URL, the API was attempting http://openclaw-workspace.agents.svc.cluster.local:8080 and retrying, causing /workspace/status and related endpoints to stall for ~4s when no workspace service exists.

Validation

• npm test -- src/services/openclawWorkspaceClient.test.js

Fixes #2

[kalinon]

This may not be needed if we are requiring mosbot-workspace-server for mosbot to function. Which i think it is.

[moltar-bot]

Superseded by #13 (same changes from moltar-forge fork).