Step 20d/23 (Phase 6): Testing — Add e2e scripts + CI matrix (all platforms)

[Jordan231111]

Summary

Create end-to-end test scripts that exercise the compiled binary through a full user workflow, and update CI to run all tests on a platform matrix.

Depends On: Steps 20a-20c (unit + integration tests)
Parent Issue: #16 (Comprehensive Testing)

Key Changes

1. Create `tests/e2e_test.sh` (Linux/macOS):
   • Build the binary
   • Run `hash` on a known file, verify output
   • Run `scan` on a clean directory, verify exit 0
   • Create EICAR test file, scan, verify detection + exit 2
   • Run `quarantine-file` on detected file, verify it moves
   • Run `list-quarantined`, verify it appears
   • Run `restore`, verify file returns
   • Clean up
2. Create `tests/e2e_test.ps1` (Windows) — equivalent workflow in PowerShell
3. Update `.github/workflows/` CI to:
   • Run on matrix: ubuntu-latest, macos-latest, windows-latest
   • Steps: fmt check → clippy → unit tests → integration tests → doc tests → e2e script
   • Run ignored tests explicitly: `cargo test -- --ignored`
4. Ensure `cargo audit` runs in CI

Acceptance Criteria

• E2E script tests the full scan → quarantine → restore workflow
• E2E script works on Linux/macOS (bash) and Windows (PowerShell)
• CI matrix runs on ubuntu-latest, macos-latest, windows-latest
• CI runs: fmt, clippy, test (normal + ignored), doc tests, e2e
• `cargo audit` runs in CI
• EICAR detection is verified end-to-end in e2e script
• All CI checks pass on all three platforms