ci: exclude external libraries from Slither analysis

- Add --filter-paths to ignore lib/, test/, script/, and mock/ directories
- Prevents false positives from Chainlink and forge-std dependencies
- Keeps Slither report focused on core protocol code (src/)
- Standard practice in audited projects with external libs
- CI remains green while maintaining security visibility

Author: tr-Kalyan

.github/workflows/audit.yml

@@ -29,5 +29,5 @@ jobs:
         uses: crytic/slither-action@v0.4.0
         with:
           fail-on: none
-          slither-args: --checklist
+          slither-args: --checklist --filter-paths "lib/|test/|script/|mock/"
           ignore-compile: true