fix: resolve symlinks in Instance cache to prevent duplicate contexts (#16651)

Co-authored-by: LukeParkerDev <10430890+Hona@users.noreply.github.com>

packages/opencode/src/util/filesystem.ts

@@ -114,8 +114,16 @@ export namespace Filesystem {
   }
 
   // We cannot rely on path.resolve() here because git.exe may come from Git Bash, Cygwin, or MSYS2, so we need to translate these paths at the boundary.
+  // Also resolves symlinks so that callers using the result as a cache key
+  // always get the same canonical path for a given physical directory.
   export function resolve(p: string): string {
-    return normalizePath(pathResolve(windowsPath(p)))
+    const resolved = pathResolve(windowsPath(p))
+    try {
+      return normalizePath(realpathSync(resolved))
+    } catch (e) {
+      if (isEnoent(e)) return normalizePath(resolved)
+      throw e
+    }
   }
 
   export function windowsPath(p: string): string {