ci: audit and harden GitHub Actions workflows

- Bump all actions to latest versions (checkout@v6, upload-artifact@v7,
  download-artifact@v8, labeler@v6, gh-release@v3, gpg-import@v7)
- Replace fragile curl|bash tool install with taiki-e/install-action@v2
- Fix Swatinem/rust-cache ordering: must run AFTER toolchain install
  for correct cache key derivation
- Add --all-targets to clippy (CI now matches local testing)
- Add RUSTDOCFLAGS=-D warnings to doc step (fail on broken links)
- Fix ARM64 build order: install Rust toolchain before adding target
  and configuring linker
- Add rust-toolchain.toml pinning Rust 1.94.0 for deterministic builds
- Update Cargo.lock: rustls-webpki v0.103.11->v0.103.13 (fixes 3 CVEs)
- Fix softprops/action-gh-release@v3: include checksums in files list
  (v3 removed the checksum input parameter)
- Fix clippy manual_checked_ops lint in screenshot.rs
- Clean up trailing whitespace and missing newlines in YAML files

.github/workflows/quality.yml

@@ -14,24 +14,30 @@ jobs:
   quality-checks:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: Swatinem/rust-cache@v2
-      
+      - uses: actions/checkout@v6
+
       - uses: ./.github/actions/deps
-      
+
       - name: Install Rust with tools
         uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt, clippy
-      
+
+      - uses: Swatinem/rust-cache@v2
+
       - name: Check formatting
         run: cargo fmt -- --check
-      
+
       - name: Run clippy
-        run: cargo clippy -- -D warnings
-      
-      - name: Run unit tests
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: Run unit tests (default features)
         run: cargo test --quiet
-      
+
+      - name: Run unit tests (all features)
+        run: cargo test --all-features --quiet
+
       - name: Check documentation
-        run: cargo doc --no-deps --document-private-items
+        env:
+          RUSTDOCFLAGS: -D warnings
+        run: cargo doc --no-deps --document-private-items