Add suggestions endpoints

[ethanpalm]

Documentation changes

This PR adds pages for the two new suggestion endpoints.

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✅ Technical accuracy

• Code examples work as written
• Commands and configurations are correct
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• Prerequisites and requirements are accurate

✅ Clarity and completeness

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Note

Low Risk
Documentation/OpenAPI-spec-only changes; risk is limited to incorrect endpoint/schema details or broken doc links/navigation.

Overview
Documents two new admin API endpoints for agent suggestions: GET /autopilot/{projectId}/suggestions (paginated list with optional status filter) and GET /autopilot/{projectId}/suggestions/count (count with optional status filter).

Updates admin-openapi.json with the new paths plus AgentSuggestion/Error schemas, and wires the new MDX reference pages into api/introduction.mdx and the API reference navigation in docs.json.

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