Add SDK support for workspace connector skill docs

[pkozikow]

The new Cloud workspace connector documentation endpoint needs typed SDK support when its public specification is published.

Platform implementation: https://github.com/airbytehq/airbyte-platform-internal/pull/19464.

Add GET /v1/workspaces/{workspaceId}/skills/docs under the Workspaces SDK group (getSkillDocs alias). Require id=connector-source:<source-instance-UUID>; accept an optional exact section from the default response outline. The identifier is a source instance UUID, not a connector definition ID.

Preserve the complete typed response: metadata, outline, nullable section_id, and content; metadata includes freshness and warnings. Support all five content block variants (heading, paragraph, list, code, table), explicit nullable fields, empty arrays, and kind=connector_source only. Library skills are excluded.

This read-only endpoint returns YAML-derived documentation, which can describe capabilities outside Cloud source execution's current scope. Reading docs grants no execution access. Availability is controlled and defaults off; workspace reader access, existing Agents enrollment, and source enablement are required. Handle sanitized problem responses for 401, 403, 404, 413, 422, 501, 502, 503, and 504.

• Regenerate from the published api_sdk.yaml and expose the Workspaces operation and typed models.
• Add wire tests for default docs and exact-section requests, all five block variants, explicit nulls, empty arrays, warnings, and sanitized problem responses.
• Coordinate the SDK release with public-spec publication and Cloud rollout.

Paired E2E remains pending. This issue tracks generation and release; it does not claim an SDK release or production activation.