Add APIs for system-level MCP servers to power Nanobot hooks

[g-linville]

Nanobot will soon have a hooks feature, which will allow the user to specify specific tool calls that should be made before or after other tool calls. We will utilize this to replace the existing webhooks feature in Obot. Our current webhooks feature just uses HTTP, but this will utilize MCP tool calls.

We need to have a separate catalog/registry for hook MCP servers that are deployed on behalf of Obot itself, rather than on behalf of a particular user. This is similar to the dispatcher pattern that we have for GPTScript daemon tools.

I believe there shouldn't be any new API types required for this, but there will likely be a new spec field on the MCPServerCatalogEntry and MCPServer types to designate whether a particular catalog entry or server is for the system, rather than for users. They will be excluded from all user-facing APIs and will not be deployable by ordinary users.

We will likely have a catalog repo similar to our existing obot-platform/mcp-catalog repo to store the hooks that we will ship.

[cjellick]

Important points from my view point (I wrote these to share wtih darren so i figured id drop in here as well):

• these will theyll be developed as independent mcp servers (meaning not directly in the obot go codebase). This lets us use the right language for the job for each one and also will give us the flexibility around including them in different distributions
• i envision the ux being that the admin can turn these on and from there administer/operate them more or less like obot-deployed mcp servers. meaning they can see their logs, restart them, etc
• first pass is doing "built in" ones, like i said, but i think we'll extend this pattern for custom ones as well. meaning, i want to expose "just right an mcp server" and we'll deploy and manage it for you as the primary way for admins to create new filters. so i want to either deprecate or at least downplay writing webhooks. ...i may not be able to deprecate it, we'll seee on that front.

[g-linville]

Moved to Stalled Out due to changed priorities.

cc @cjellick