Update toolhive-core to v0.0.16 (#714)

## Summary

- Bump `toolhive-core` from v0.0.15 to v0.0.16
- Picks up stacklok/toolhive-core#86 which embeds all
externally-referenced JSON schemas so `$ref` resolution during
validation never makes HTTP requests

This fixes the sync timeout reported by Peder in network-restricted
environments where egress to `raw.githubusercontent.com` and
`static.modelcontextprotocol.io` is blocked by network policy.

## Test plan

- [x] `task all` passes (lint, tests, build)
- [ ] Deploy to a network-restricted environment and verify sync
completes without schema fetch timeouts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rdimitrov

go.mod

@@ -22,7 +22,7 @@ require (
 	github.com/spf13/cobra v1.10.2
 	github.com/spf13/viper v1.21.0
 	github.com/stacklok/toolhive v0.19.0
-	github.com/stacklok/toolhive-core v0.0.15
+	github.com/stacklok/toolhive-core v0.0.16
 	github.com/stretchr/testify v1.11.1
 	github.com/swaggo/swag/v2 v2.0.0-rc5
 	github.com/testcontainers/testcontainers-go v0.42.0

go.sum

@@ -590,8 +590,8 @@ github.com/spf13/viper v1.21.0 h1:x5S+0EU27Lbphp4UKm1C+1oQO+rKx36vfCoaVebLFSU=
 github.com/spf13/viper v1.21.0/go.mod h1:P0lhsswPGWD/1lZJ9ny3fYnVqxiegrlNrEmgLjbTCAY=
 github.com/stacklok/toolhive v0.19.0 h1:DAqiFHmwoe3BwPA9yElrBn2S6x0k6UnrgyBaI5M8ECs=
 github.com/stacklok/toolhive v0.19.0/go.mod h1:hLMReQs7U85lXv4gs9Kd5id3DFJx9JB0oFrMapvLkmU=
-github.com/stacklok/toolhive-core v0.0.15 h1:uhkB4knchTZc6zOiVUHfJe7R/qxrshvhww6HVeFVfIg=
-github.com/stacklok/toolhive-core v0.0.15/go.mod h1:6KW90AxiKnB2bu70L4qa3sKjHFaUi2lgl8bmPj1Q16g=
+github.com/stacklok/toolhive-core v0.0.16 h1:Td/o/zrO3Pbr6tkx4r0k8Bqn9DySlwgah2vknE8tj5A=
+github.com/stacklok/toolhive-core v0.0.16/go.mod h1:iHp39rCHZxXzU5FmXKK9aoH48NE+K0ob+MtdTS9CvAk=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.2.0/go.mod h1:qt09Ya8vawLte6SNmTgCsAVtYtaKzEcn8ATUoHMkEqE=