fix: additionalProperties in push_files schema (#2011)

Some MCP clients require array item schemas to explicitly set
`additionalProperties: false`. Without this, `push_files` calls will fail.

Fixes #2011
Research and fix was initially done by @04cb

Author: sierikov

pkg/github/__toolsnaps__/push_files.snap

@@ -12,6 +12,7 @@
       "files": {
         "description": "Array of file objects to push, each object with path (string) and content (string)",
         "items": {
+          "additionalProperties": false,
           "properties": {
             "content": {
               "description": "file content",

pkg/github/repositories.go

@@ -1233,7 +1233,8 @@ func PushFiles(t translations.TranslationHelperFunc) inventory.ServerTool {
 						Type:        "array",
 						Description: "Array of file objects to push, each object with path (string) and content (string)",
 						Items: &jsonschema.Schema{
-							Type: "object",
+							Type:                 "object",
+							AdditionalProperties: &jsonschema.Schema{Not: &jsonschema.Schema{}},
 							Properties: map[string]*jsonschema.Schema{
 								"path": {
 									Type:        "string",