Remove remaining subflake references from workflows and docs

Co-authored-by: blaggacao <[email protected]>

Author: Copilot

.github/copilot-instructions.md

@@ -227,7 +227,6 @@ mdbook serve            # Serve docs locally at localhost:3000
 - **Slow builds**: This is normal for Nix - do not cancel, builds are cached after first success
 - **direnv not working**: Ensure direnv is installed and shell hook is configured
 - **Network errors during setup**: Some dependencies require internet access; check firewall/proxy settings
-- **Flake lock issues**: In subflakes, run `./.github/workflows/update-subflake.sh` to update lock files
 - **"error: getting status of '/nix/store/...'**: Usually means incomplete download; try `nix build` again
 - **Out of disk space**: Nix store can get large; run `nix-collect-garbage` to clean up
 

.github/workflows/gh-pages.yaml

@@ -15,9 +15,6 @@ jobs:
 
       - uses: nixbuild/nix-quick-install-action@v25
 
-      - name: Update subflake references
-        run: ./.github/workflows/update-subflake.sh
-
       - run: nix develop .#book -c mdbook build ./.
 
       - name: Deploy