chore: Release server.json schema version 2025-12-11 (#841)

Prepared by Claude Code, iterated and reviewed by me.

## Summary

This PR releases the server.json schema version `2025-12-11`,
incorporating URL template variables for remote servers from #570.

### What's New

- **URL Template Variables for Remote Servers** - Remote servers can now
define configurable variables in URLs using `{curly_braces}` notation,
enabling multi-tenant deployments.

### Schema Version
- `2025-10-17` → `2025-12-11`

## Release Sequence

1. ~~**First: Merge static repo PR** -
https://github.com/modelcontextprotocol/static/pull/11 (publishes schema
to versioned URL)~~
2. **Then: Merge this PR** - Updates registry code to reference the new
schema version

## Changes in This PR

- [x] Update CHANGELOG.md with release notes
- [x] Update `CurrentSchemaVersion` in `pkg/model/constants.go`
- [x] Update schema example URL in `docs/reference/api/openapi.yaml`
- [x] Update schema URL in `pkg/api/v0/types.go`
- [x] Update all documentation examples to use new schema version
- [x] Regenerate `server.schema.json`

## Test Plan
- [x] `make check` passes (lint, schema validation, example validation)
- [x] Unit tests pass for validators and publisher commands

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

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

docs/modelcontextprotocol-io/package-types.mdx

@@ -15,7 +15,7 @@ npm packages use `"registryType": "npm"` in `server.json`. For example:
 
 ```json server.json highlight={9}
 {
-  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json",
+  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.username/email-integration-mcp",
   "title": "Email Integration",
   "description": "Send emails and manage email accounts",
@@ -53,7 +53,7 @@ PyPI packages use `"registryType": "pypi"` in `server.json`. For example:
 
 ```json server.json highlight={9}
 {
-  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json",
+  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.username/database-query-mcp",
   "title": "Database Query",
   "description": "Execute SQL queries and manage database connections",
@@ -91,7 +91,7 @@ NuGet packages use `"registryType": "nuget"` in `server.json`. For example:
 
 ```json server.json highlight={9}
 {
-  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json",
+  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.username/azure-devops-mcp",
   "title": "Azure DevOps",
   "description": "Manage Azure DevOps work items and pipelines",
@@ -135,7 +135,7 @@ Docker/OCI images use `"registryType": "oci"` in `server.json`. For example:
 
 ```json server.json highlight={9}
 {
-  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json",
+  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.username/kubernetes-manager-mcp",
   "title": "Kubernetes Manager",
   "description": "Deploy and manage Kubernetes resources",
@@ -170,7 +170,7 @@ MCPB packages use `"registryType": "mcpb"` in `server.json`. For example:
 
 ```json server.json highlight={9}
 {
-  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json",
+  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.username/image-processor-mcp",
   "title": "Image Processor",
   "description": "Process and transform images with various filters",