feat(tests): update testing paths for deterministic integration tests

- Modified test data paths in various integration tests to use the Spacedrive source code instead of user directories, ensuring consistent and deterministic test results across environments.
- Updated comments and documentation to reflect the new testing approach and clarify the purpose of using project source code for testing.
- Enhanced the GitHub Actions workflow to skip Rust toolchain setup on macOS self-hosted runners, assuming Rust is pre-installed.

.github/workflows/core_tests.yml

@@ -53,12 +53,16 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
+      # Skip Rust toolchain setup on self-hosted runners (macOS)
+      # Assumes Rust is pre-installed and maintained on self-hosted machines
       - name: Setup Rust
+        if: ${{ matrix.settings.os != 'macos' }}
         uses: dtolnay/rust-toolchain@stable
         with:
           targets: ${{ matrix.settings.target }}
 
       - name: Setup System and Rust
+        if: ${{ matrix.settings.os != 'macos' }}
         uses: ./.github/actions/setup-system
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
@@ -82,6 +86,8 @@ jobs:
           path: target
           key: ${{ matrix.settings.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
 
+      # Native deps setup is fast on self-hosted if deps already cached in apps/.deps/
+      # Keep it to ensure correct versions even on self-hosted runners
       - name: Setup native dependencies
         run: cargo xtask setup