Fix CI: install libfuse3-dev so Makefile parses on Ubuntu

detect_fuse.sh runs at Makefile parse time; without fuse headers the
$(error) fires before any target runs. Adding libfuse3-dev unblocks
make tests (test binaries themselves don't link fuse).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Install build dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y build-essential
+          sudo apt-get install -y build-essential libfuse3-dev
 
       - name: Build test binaries
         run: make tests