fix(coding-agent): dedupe symlinked resources (#3818)

* fix(coding-agent): dedupe symlinked resources

Fixes #3767

* refactor(coding-agent): extract canonicalizePath util for symlink resolution

packages/coding-agent/src/utils/paths.ts

@@ -1,3 +1,19 @@
+import { realpathSync } from "node:fs";
+
+/**
+ * Resolve a path to its canonical (real) form, following symlinks.
+ * Falls back to the raw path if resolution fails (e.g. the target does
+ * not exist yet), so that callers never crash on missing filesystem
+ * entries.
+ */
+export function canonicalizePath(path: string): string {
+	try {
+		return realpathSync(path);
+	} catch {
+		return path;
+	}
+}
+
 /**
  * Returns true if the value is NOT a package source (npm:, git:, etc.)
  * or a URL protocol. Bare names and relative paths without ./ prefix