ci: clean workspace artifacts before cache upload

Run `cargo clean --workspace` at the end of each cached job so that
only compiled dependencies are cached, not the workspace's own build
artifacts. This reduces cache size and upload/download time while
keeping the expensive dependency compilation cached.

https://claude.ai/code/session_014NgdhJMEQSguQ8yXAuTfnq

Author: claude

.github/workflows/benchmark.yaml

@@ -115,3 +115,7 @@ jobs:
 
       - name: Check for performance regressions
         run: node ci/github-actions/check-for-performance-regressions.js
+
+      - name: Clean workspace artifacts before cache
+        shell: bash
+        run: cargo clean --workspace

.github/workflows/clippy.yaml

@@ -58,3 +58,8 @@ jobs:
           BUILD: 'false'
           TEST: 'false'
         run: ./test.sh
+
+      - name: Clean workspace artifacts before cache
+        if: matrix.os != 'macos-latest'
+        shell: bash
+        run: cargo clean --workspace

.github/workflows/deploy.yaml

@@ -616,3 +616,7 @@ jobs:
           asset_path: ./tmp.benchmark-reports.tar.gz
           asset_name: benchmark-reports.tar.gz
           asset_content_type: application/x-compressed-tar
+
+      - name: Clean workspace artifacts before cache
+        shell: bash
+        run: cargo clean --workspace

.github/workflows/test.yaml

@@ -73,3 +73,8 @@ jobs:
           BUILD_FLAGS: '--locked'
           TEST_FLAGS: '--no-fail-fast'
         run: ./test.sh --release
+
+      - name: Clean workspace artifacts before cache
+        if: matrix.os != 'macos-latest'
+        shell: bash
+        run: cargo clean --workspace