refactor: remove Groq and Cerebras support

[antonvishal]

Summary

Remove native Groq and Cerebras support from the current SDKs, protocol, extension, eval configuration, and documentation.

These integrations appear stale. Keeping this PR as a draft so maintainers can decide whether the removal should move forward.

Validation

1. Extension: 354 tests passed
2. Integration core: 32 tests passed
3. Python SDK: 529 passed, 1 skipped
4. Go SDK and generated-artifact checks passed
5. Workspace formatting, lint, and TypeScript checks passed

---

Summary by cubic

Removes native Groq and Cerebras provider support from the SDK, protocol, extension, and docs because these integrations are stale and add maintenance burden. This is a breaking change for anyone using these providers.

Migration

• Move to openai, anthropic, or google, or use the bring-your-own-LLM callback.

^{Written for commit 57bfdee. Summary will update on new commits.}

[changeset-bot]

🦋 Changeset detected

Latest commit: 57bfdee

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 20 packages

Name	Type
@browserbasehq/stagehand-protocol	Major
@browserbasehq/stagehand-extension	Patch
@browserbasehq/stagehand-python	Patch
@browserbasehq/stagehand-go	Patch
@browserbasehq/stagehand	Patch
@browserbasehq/stagehand-integrations	Patch
@browserbasehq/stagehand-integrations-example-eve-facade	Patch
@browserbasehq/stagehand-integrations-example-pi-facade	Patch
@browserbasehq/stagehand-integrations-claude-agent-sdk	Patch
@browserbasehq/stagehand-integrations-example-claude-code-facade	Patch
@browserbasehq/stagehand-integrations-codex-sdk	Patch
@browserbasehq/stagehand-integrations-example-codex-facade	Patch
@browserbasehq/stagehand-integrations-cursor-sdk	Patch
@browserbasehq/stagehand-integrations-deepagents-sdk	Patch
@browserbasehq/stagehand-integrations-eve-sdk	Patch
@browserbasehq/stagehand-integrations-fx-sdk	Patch
@browserbasehq/stagehand-integrations-mastra-sdk	Patch
@browserbasehq/stagehand-integrations-example-mastra-facade	Patch
@browserbasehq/stagehand-integrations-pi-sdk	Patch
@browserbasehq/stagehand-integrations-example-vercel-ai-facade	Patch

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[github-actions]

This PR is from an external contributor and must be approved by a stagehand team member with write access before CI can run.
Approving the latest commit mirrors it into an internal PR owned by the approver.
If new commits are pushed later, the internal PR stays open but is marked stale until someone approves the latest external commit and refreshes it.