feat: AgentToolProvider reconciler for cross-cluster MCP tool federation

[jordigilh]

Context

Not one of the customer's 3 named MVPs, but a forward-looking differentiator in the same demo catalog: an agent connected to one gateway transparently calling tools hosted behind a different cluster.

The hard part is already built and tested — praxis-ai's data-plane MCP gateway/broker behavior (tool-catalog aggregation + cross-cluster tools/call routing) exists, tracked by:

• ai#155, ai#205, ai#173 (all open, unassigned, milestone v0.2.0)

But Grid's AgentToolProvider CRD exists with zero controller/reconciler logic — nothing wires it up on the Grid side.

Scope

Add a controller/reconciler for AgentToolProvider, mirroring the already-proven InferenceProvider reconciliation pipeline.

Estimate

~8-13 days, control-plane only (cross-link ai#155/#205/#173 for the data-plane side, which is not in scope here).

[jordigilh]

Opened #56 with the Grid-side control plane: MCP probe client + reconciler + Helm/E2E scaffolding, validated against a real kind cluster (both the healthy-convergence and unreachable-endpoint paths). Data-plane MCP tool-catalog aggregation and cross-cluster tools/call routing (praxis-ai#155, #205, #173) remain out of scope, per this issue's stated scope.