Add GLM provider support and contributor guidance

[webup]

What

Add GLM/Z.AI as a native model provider in ClawMaster. The setup wizard and Models page now expose GLM directly, persist the OpenClaw zai provider config, and use live model catalog discovery in both desktop and web runtimes.

Why

Users should not need to configure GLM through the generic custom OpenAI-compatible provider path. A native provider entry gives them the right API-key link, base URL, fallback model list, validation flow, and default model references.

How

• Add zai to the shared provider catalog used by the setup wizard and Models page
• Allow Z.AI live model catalog requests in both frontend and backend catalog helpers
• Filter non-chat entries from GLM model catalog responses
• Add focused tests for provider setup, Models UI behavior, catalog requests, and persisted config
• Document the provider integration workflow in CONTRIBUTING.md

Testing

• npx vitest run src/shared/providerCatalog.test.ts src/modules/setup/tests/realAdapter.test.ts src/modules/setup/tests/SetupWizard.test.tsx src/modules/models/tests/ModelsPage.test.tsx from packages/web
• npm test --workspace=@openclaw-manager/backend
• npm run build --workspace=@openclaw-manager/backend
• npm run build --workspace=@openclaw-manager/web

Screenshots

Not included. This PR adds a provider option in existing setup/model surfaces; no layout change beyond the new GLM provider entry.