chore: fix cross-platform path check in classifyWriteEdit

Remove POSIX-only startsWith('/') guard so absolute Windows paths
(e.g. C:\Users\...) are no longer auto-allowed outside the project root.
Now relies solely on resolvedPath.startsWith(process.cwd()) and uses
path.sep for node_modules detection, making the check portable.

Author: amondnet

plugins/gatekeeper/dist/pre-tool-use.js

@@ -218,7 +218,7 @@ function classifyWriteEdit(filePath) {
     }
   }
   const resolvedPath = path.resolve(filePath);
-  if (!resolvedPath.startsWith("/") || resolvedPath.startsWith(process.cwd()) || resolvedPath.includes("/node_modules/")) {
+  if (resolvedPath.startsWith(process.cwd()) || resolvedPath.includes(`${path.sep}node_modules${path.sep}`)) {
     return { decision: "allow", reason: "Safe project file write" };
   }
   return null;

plugins/gatekeeper/src/pre-tool-use.ts

@@ -151,9 +151,9 @@ export function classifyWriteEdit(filePath: string): { decision: Decision, reaso
     }
   }
 
-  // Project-relative paths are generally safe; resolve to absolute path first to prevent path traversal
+  // Resolve to absolute path first to prevent path traversal; allow only within project root
   const resolvedPath = path.resolve(filePath)
-  if (!resolvedPath.startsWith('/') || resolvedPath.startsWith(process.cwd()) || resolvedPath.includes('/node_modules/')) {
+  if (resolvedPath.startsWith(process.cwd()) || resolvedPath.includes(`${path.sep}node_modules${path.sep}`)) {
     return { decision: 'allow', reason: 'Safe project file write' }
   }