HYDI-23: Support for MCP servers

[kasperwelner]

Implements HYDI-23

Changes

• Added an MCP Servers JSON field to the project config form (/config/new, /config/:projectKey).
• Added client-side JSON linting/validation that blocks save on invalid input and shows line-numbered parse errors.
• Added server-side validation for mcp_servers input to reject invalid JSON/object payloads.
• Persisted mcp_servers in project configs (JSONB column), including migration and query-layer updates.
• Wired project-level mcp_servers into Oz agent spawn config when creating runs.
• Updated docs for configuration, schema, worker spawning behavior, and config UI.

Co-Authored-By: Oz oz-agent@warp.dev

Conversation: https://app.warp.dev/conversation/87065356-cb04-4755-8b2d-4568b3fa9049
Run: https://oz.warp.dev/runs/019e01b7-67c6-74e8-8e15-8bc1e75ff3eb
This PR was generated with Oz.