fix(ci): replace rustsec/audit-check with actions-rust-lang/audit (#438)

The rustsec/audit-check@v2 action was failing with exit code 101 when
trying to install cargo-audit. This was caused by cargo install
compilation failures in the CI environment.

Switch to actions-rust-lang/audit@v1, which is a more actively
maintained alternative that:
- Explicitly installs Rust stable toolchain before cargo-audit
- Provides better summary reports with vulnerability details
- Is actively maintained (last updated Jan 2026)
- Has proper handling of cargo-audit installation

Also updated permissions from 'checks: write' to 'issues: write'
as required by the new action.

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt

.github/workflows/ci.yml

@@ -268,22 +268,16 @@ jobs:
     name: Security Audit
     runs-on: blacksmith-4vcpu-ubuntu-2404
     permissions:
-      checks: write
       contents: read
+      issues: write
     steps:
       - uses: actions/checkout@v4
 
-      - name: Cache cargo-audit (Blacksmith 4x faster cache)
-        uses: actions/cache@v4
-        with:
-          path: |
-            ~/.cargo/bin/cargo-audit
-            ~/.cargo/advisory-db
-          key: cargo-audit-${{ runner.os }}
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
 
-      - uses: rustsec/audit-check@v2
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: actions-rust-lang/audit@v1
+        name: Audit Rust Dependencies
 
   # ==========================================================================
   # Final status check (for branch protection) - lightweight - 4 vCPU