perf: optimize CI workflows with caching and reduced parallelism

Changes:
- Add Rust caching (Swatinem/rust-cache) to all heavy build jobs
- Reduce cargo-check-each-crate from 7 to 4 parallel jobs
- Reduce tests-linux-stable matrix from 6 to 3 jobs
- Set CARGO_INCREMENTAL=0 for consistent caching
- Reduce timeouts from 60 to 45 minutes (cache makes builds faster)
- Remove redundant disk cleanup steps (cache handles this)

Expected improvements:
- 50-80% faster builds after cache is populated
- Lower VPS load (fewer parallel jobs)
- More consistent build times

Affected workflows:
- checks.yml (cargo-clippy, check-try-runtime)
- tests.yml (quick-benchmarks, cargo-check-all-benches)
- tests-misc.yml (test-pezframe-ui, cargo-check-each-crate)
- tests-linux-stable.yml (test-linux-stable)
- docs.yml (test-doc, build-rustdoc)

.github/workflows/docs.yml

@@ -21,42 +21,48 @@ jobs:
 
   test-doc:
     runs-on: ${{ needs.preflight.outputs.RUNNER }}
-    timeout-minutes: 60
+    timeout-minutes: 45
     needs: [preflight]
     container:
       image: ${{ needs.preflight.outputs.IMAGE }}
+    env:
+      RUSTFLAGS: "-Cdebug-assertions=y -Dwarnings"
+      SKIP_WASM_BUILD: 1
+      CARGO_INCREMENTAL: 0
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
-      - name: Clean cargo cache to free disk space
-        run: |
-          cargo clean 2>/dev/null || true
-          rm -rf ~/.cargo/registry/cache 2>/dev/null || true
-          rm -rf ~/.cargo/git/db 2>/dev/null || true
+
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
+        with:
+          shared-key: test-doc
+          cache-on-failure: true
+
       - run: cargo test --doc --workspace --locked --all-features
         id: required
-        env:
-          RUSTFLAGS: "-Cdebug-assertions=y -Dwarnings"
-          SKIP_WASM_BUILD: 1
 
   build-rustdoc:
     runs-on: ${{ needs.preflight.outputs.RUNNER }}
-    timeout-minutes: 60
+    timeout-minutes: 45
     if: ${{ needs.preflight.outputs.changes_rust }}
     needs: [preflight]
     container:
       image: ${{ needs.preflight.outputs.IMAGE }}
+    env:
+      SKIP_WASM_BUILD: 1
+      CARGO_INCREMENTAL: 0
+      RUSTDOCFLAGS: "-Dwarnings --default-theme=ayu --html-in-header ./docs/sdk/assets/header.html --extend-css ./docs/sdk/assets/theme.css --html-after-content ./docs/sdk/assets/after-content.html"
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
-      - name: Clean cargo cache to free disk space
-        run: |
-          cargo clean 2>/dev/null || true
-          rm -rf ~/.cargo/registry/cache 2>/dev/null || true
-          rm -rf ~/.cargo/git/db 2>/dev/null || true
+
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
+        with:
+          shared-key: build-rustdoc
+          cache-on-failure: true
+
       - run: cargo doc --all-features --workspace --no-deps --locked
         id: required
-        env:
-          SKIP_WASM_BUILD: 1
-          RUSTDOCFLAGS: "-Dwarnings --default-theme=ayu --html-in-header ./docs/sdk/assets/header.html --extend-css ./docs/sdk/assets/theme.css --html-after-content ./docs/sdk/assets/after-content.html"
       - run: rm -f ./target/doc/.lock
       - run: mv ./target/doc ./crate-docs
       - name: Inject Simple Analytics script