[connectors] Generic tool-call API + MCP auto-generation

[serge-ivo]

[connectors] Generic tool-call API + MCP auto-generation

Make every registry tool callable uniformly by any client, not just the agent LLM.

Do

• POST /v1/instances/:id/tools/:name (owner/permission-scoped) — invoke any tool the instance is allowed, with a JSON body validated against the tool's schema. Same dispatch path as the runtime loop.
• MCP: auto-generate server.tool() registrations from the registry (from the registry issue) so external MCP clients get the same connector tools with the same names/schemas.
• Audit every invocation (build on the [Admin] Foundation: access control gating + admin-action audit log #28 admin audit log); rate-limit like other /v1/* routes.

Acceptance

• A connector tool is callable via runtime, MCP, and POST …/tools/:name with identical behavior + schema.
• Not-allowed / not-connected / not-granted → clear 4xx; audited.
• Tests for gate + dispatch + schema validation.

Depends on the tool-registry + connector-framework issues.

[serge-ivo]

Shipped — generic tool-call API (routes/tools.ts) + MCP instance-tools (workers/mcp/src/instance-tools/*). All registry tools surface on all three planes.