chore: replace GitHub MCP server with official implementation and add HTTP installation method

- Remove archived ModelContextProtocol GitHub server
- Add official GitHub MCP server from github/github-mcp-server
- Add HTTP installation method to registry schema with URL and optional headers support
- Configure HTTP as recommended installation method for GitHub server
- Add GITHUB_BASE_URL to Go and Docker installation methods for GitHub Enterprise support

Author: niechen

mcp-registry/schema/server-schema.json

@@ -217,9 +217,24 @@
       "additionalProperties": {
         "type": "object",
         "required": [
-          "type",
-          "command",
-          "args"
+          "type"
+        ],
+        "allOf": [
+          {
+            "if": {
+              "properties": {
+                "type": {
+                  "const": "http"
+                }
+              }
+            },
+            "then": {
+              "required": ["url"]
+            },
+            "else": {
+              "required": ["command", "args"]
+            }
+          }
         ],
         "properties": {
           "type": {
@@ -231,7 +246,8 @@
               "docker",
               "cli",
               "uvx",
-              "custom"
+              "custom",
+              "http"
             ]
           },
           "command": {
@@ -263,6 +279,17 @@
           "recommended": {
             "type": "boolean",
             "description": "Whether this is the recommended installation method"
+          },
+          "url": {
+            "type": "string",
+            "description": "URL to fetch the server binary from (required for http type)"
+          },
+          "headers": {
+            "type": "object",
+            "description": "HTTP headers to send with the request (optional for http type)",
+            "additionalProperties": {
+              "type": "string"
+            }
           }
         }
       }