docs: link v4 integrations overview from the v3 migration guide

[HaoChiBao]

Summary

• Replace the stale TODO: Link to agent integrations overview page in packages/docs/v4/migrations/v3.mdx.
• Point readers who wrapped Stagehand in an agent framework to /v4/integrations/overview.

Test plan

• Open /v4/migrations/v3 and confirm the new sentence links to the integrations overview
• Confirm /v4/integrations/overview exists in the docs nav

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Summary by cubic

Links the v4 integrations overview from the v3 migration guide where a TODO placeholder existed. Previously, readers who wrapped Stagehand in an agent framework had no next step; now we direct them to /v4/integrations/overview to reduce confusion.

Review

• Open /v4/migrations/v3 and verify the new link points to /v4/integrations/overview.
• Confirm /v4/integrations/overview exists in the docs nav.

^{Written for commit 14fd173. Summary will update on new commits.}

[changeset-bot]

⚠️ No Changeset found

Latest commit: 14fd173

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[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}