feat(docs): add support for terraform

[ematipico]

Summary

Add Stainless-generated Terraform documentation to API operation pages, including fields, nested attributes, and HCL examples.

• Add generate-terraform-docs.ts to map Stainless Terraform declarations to Forge OpenAPI operations.
• Commit the generated Terraform documentation index.
• Preserve multiple Terraform declarations associated with the same API operation.
• Render required, optional, computed, and nested Terraform fields.
• Pair each declaration with its own sticky HCL sample card.
• Include Terraform examples in agent-facing Markdown.
• Show fallback messaging for operations without Terraform support.

UI

• Render required, optional, computed, and nested Terraform fields.
• Display deprecated, sensitive, and replacement-triggering field metadata.
• Pair every Terraform declaration with its own HCL sample card and target selector.
• Keep each sample card sticky within its corresponding declaration section.
• Wrap long HCL lines and avoid nested scrollbars.
• Hide unrelated HTTP responses while viewing Terraform documentation.
• Show a fallback when an API operation has no Terraform implementation.

Generated Coverage

• 664 mapped API operations
• 673 Terraform declarations
• 48 unmatched declarations
• 4 declarations without generated snippets

Validation

• Add generator and endpoint-normalization tests.
• Add extension-data, multi-declaration, and Markdown-target tests.
• Verify all 122 docs-site tests pass.
• Verify pnpm --filter docs-site check.
• Verify pnpm --filter docs-site build.
• Preview-test mapped, unmapped, and multi-declaration Terraform pages.