ci: skip LFS in Copilot cloud agent checkout

The Copilot cloud agent job fails during its internal clone because
app/assets/windows/arm64/OpenConsole.pdb is a 30 MB LFS object that
does not exist on the fork's LFS server (upstream LFS objects are not
copied to forks).

The agent only works on source files (Rust, UI, config) and has no
need for Windows ARM64 debug symbols. Adding .github/copilot/setup-steps.yml
with lfs: false tells the Copilot runtime to skip LFS hydration on checkout,
removing the failure path entirely.

Ref: 63cdd88

Author: BunsDev

.github/copilot/setup-steps.yml

@@ -0,0 +1,6 @@
+steps:
+  - name: Checkout repository (skip LFS)
+    uses: actions/checkout@v4
+    with:
+      fetch-depth: 1
+      lfs: false