Add changelog entry for cache hash portability fix

Co-authored-by: iclanton <5010588+iclanton@users.noreply.github.com>

Author: Copilot

common/changes/@rushstack/heft-typescript-plugin/fix-cache-hash-portability_2026-01-04-03-06.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/heft-typescript-plugin",
+      "comment": "Fix TypeScript build cache hash computation to use relative paths with normalized separators for portability across machines and platforms",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@rushstack/heft-typescript-plugin",
+  "email": "copilot@github.com"
+}