feat(github): always return SHA and resource for get_file_contents

Author: yonaka15

pkg/github/__toolsnaps__/get_file_contents.snap

@@ -3,7 +3,7 @@
     "title": "Get file or directory contents",
     "readOnlyHint": true
   },
-  "description": "Get the contents of a file or directory from a GitHub repository",
+  "description": "Get the contents of a file or directory from a GitHub repository. For files, this tool always returns the file content as a resource and its SHA hash.",
   "inputSchema": {
     "properties": {
       "owner": {
@@ -23,7 +23,7 @@
         "type": "string"
       },
       "sha": {
-        "description": "Accepts optional commit SHA. If specified, it will be used instead of ref",
+        "description": "Accepts optional commit SHA. If specified, it will be used to fetch the file at a specific version to avoid race conditions.",
         "type": "string"
       }
     },