fix(ci): enable sccache cache loading and saving in GitHub Actions

Previously sccache cache had 0% hit rate because environment variables
were set too late (after sccache-action execution). This caused cache to
never load or save, resulting in full compilation on every workflow run.

Changes:
- Add job-level env vars (SCCACHE_GHA_ENABLED, RUSTC_WRAPPER)
- Specify explicit sccache version v0.10.2 (required for GHA cache service)
- Remove redundant configuration steps

Expected improvement: 40-60% cache hit rate, 50-70% faster builds

Author: bug-ops

.github/workflows/ci.yml

@@ -24,6 +24,9 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         rust: [stable]
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
     steps:
       - name: Checkout code
         uses: actions/checkout@v6
@@ -35,12 +38,8 @@ jobs:
 
       - name: Setup sccache
         uses: mozilla-actions/sccache-action@v0.0.9
-
-      - name: Configure sccache
-        shell: bash
-        run: |
-          echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
-          echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+        with:
+          version: "v0.10.2"
 
       - name: Install cargo-nextest
         uses: taiki-e/install-action@nextest
@@ -70,6 +69,9 @@ jobs:
   clippy:
     name: Clippy
     runs-on: ubuntu-latest
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
     steps:
       - name: Checkout code
         uses: actions/checkout@v6
@@ -81,12 +83,8 @@ jobs:
 
       - name: Setup sccache
         uses: mozilla-actions/sccache-action@v0.0.9
-
-      - name: Configure sccache
-        shell: bash
-        run: |
-          echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
-          echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+        with:
+          version: "v0.10.2"
 
       - name: Run clippy
         run: cargo clippy --all-targets --all-features -- -D warnings
@@ -111,6 +109,9 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
     steps:
       - name: Checkout code
         uses: actions/checkout@v6
@@ -120,12 +121,8 @@ jobs:
 
       - name: Setup sccache
         uses: mozilla-actions/sccache-action@v0.0.9
-
-      - name: Configure sccache
-        shell: bash
-        run: |
-          echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
-          echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+        with:
+          version: "v0.10.2"
 
       - name: Build release
         run: cargo build --release --verbose

.github/workflows/release.yml

@@ -78,6 +78,9 @@ jobs:
     needs: validate
     runs-on: ${{ matrix.os }}
     timeout-minutes: 45
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
     strategy:
       fail-fast: false
       matrix:
@@ -135,12 +138,8 @@ jobs:
 
       - name: Setup sccache
         uses: mozilla-actions/sccache-action@v0.0.9
-
-      - name: Configure sccache
-        shell: bash
-        run: |
-          echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
-          echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+        with:
+          version: "v0.10.2"
 
       # Install musl tools for Linux musl builds
       - name: Install musl tools (Linux musl only)