feat(git-master): add configurable commit footer and co-author options

Add git_master config with commit_footer and include_co_authored_by flags.
Users can disable Sisyphus attribution in commits via oh-my-opencode.json.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

assets/oh-my-opencode.schema.json

@@ -37,7 +37,8 @@
         "type": "string",
         "enum": [
           "playwright",
-          "frontend-ui-ux"
+          "frontend-ui-ux",
+          "git-master"
         ]
       }
     },
@@ -1999,6 +2000,19 @@
           "type": "boolean"
         }
       }
+    },
+    "git_master": {
+      "type": "object",
+      "properties": {
+        "commit_footer": {
+          "default": true,
+          "type": "boolean"
+        },
+        "include_co_authored_by": {
+          "default": true,
+          "type": "boolean"
+        }
+      }
     }
   }
 }