ci: wire fsx_paranoid into the fsx job

The paranoid variant does a full CAS round-trip after each mutation
(close, wait for flush, reopen, read-back), so it catches composition
bugs in range_upload that the canonical fsx misses — staging-only fsx
reads from the local staging file, not from CAS. ~2.5 min for the
default 100 ops, gated by HF_TOKEN like the other fsx job.

Author: XciD

.github/workflows/ci.yml

@@ -121,6 +121,10 @@ jobs:
         timeout-minutes: 10
         run: cargo test --release --test fsx -- --test-threads=1 --nocapture
 
+      - name: fsx paranoid (CAS round-trip per mutation)
+        timeout-minutes: 15
+        run: cargo test --release --test fsx_paranoid -- --test-threads=1 --nocapture
+
   xfstests:
     name: xfstests (filesystem exerciser)
     runs-on: