test(ci): probe GitHub Actions sccache backend on Windows

Bump sccache to 0.10.0 and detect either ACTIONS_CACHE_URL or
ACTIONS_RESULTS_URL before enabling the GitHub backend. Add a tiny
diagnostic so the Windows logs show which Actions cache env vars are
available.

Co-authored-by: Codex <noreply@openai.com>

.github/workflows/rust-ci.yml

@@ -141,8 +141,8 @@ jobs:
       run:
         working-directory: codex-rs
     env:
-      # Speed up repeated builds across CI runs by caching compiled objects (non-Windows).
-      USE_SCCACHE: ${{ startsWith(matrix.runner, 'windows') && 'false' || 'true' }}
+      # Speed up repeated builds across CI runs by caching compiled objects.
+      USE_SCCACHE: "true"
       CARGO_INCREMENTAL: "0"
       SCCACHE_CACHE_SIZE: 10G
       # In rust-ci, representative release-profile checks use thin LTO for faster feedback.
@@ -292,14 +292,17 @@ jobs:
         uses: taiki-e/install-action@44c6d64aa62cd779e873306675c7a58e86d6d532 # v2
         with:
           tool: sccache
-          version: 0.7.5
+          version: 0.10.0
 
       - name: Configure sccache backend
         if: ${{ env.USE_SCCACHE == 'true' }}
         shell: bash
         run: |
           set -euo pipefail
-          if [[ -n "${ACTIONS_CACHE_URL:-}" && -n "${ACTIONS_RUNTIME_TOKEN:-}" ]]; then
+          echo "ACTIONS_CACHE_URL set: $([[ -n "${ACTIONS_CACHE_URL:-}" ]] && echo yes || echo no)"
+          echo "ACTIONS_RESULTS_URL set: $([[ -n "${ACTIONS_RESULTS_URL:-}" ]] && echo yes || echo no)"
+          echo "ACTIONS_RUNTIME_TOKEN set: $([[ -n "${ACTIONS_RUNTIME_TOKEN:-}" ]] && echo yes || echo no)"
+          if [[ -n "${ACTIONS_RUNTIME_TOKEN:-}" && ( -n "${ACTIONS_CACHE_URL:-}" || -n "${ACTIONS_RESULTS_URL:-}" ) ]]; then
             echo "SCCACHE_GHA_ENABLED=true" >> "$GITHUB_ENV"
             echo "Using sccache GitHub backend"
           else
@@ -506,8 +509,8 @@ jobs:
       run:
         working-directory: codex-rs
     env:
-      # Speed up repeated builds across CI runs by caching compiled objects (non-Windows).
-      USE_SCCACHE: ${{ startsWith(matrix.runner, 'windows') && 'false' || 'true' }}
+      # Speed up repeated builds across CI runs by caching compiled objects.
+      USE_SCCACHE: "true"
       CARGO_INCREMENTAL: "0"
       SCCACHE_CACHE_SIZE: 10G
 
@@ -594,14 +597,17 @@ jobs:
         uses: taiki-e/install-action@44c6d64aa62cd779e873306675c7a58e86d6d532 # v2
         with:
           tool: sccache
-          version: 0.7.5
+          version: 0.10.0
 
       - name: Configure sccache backend
         if: ${{ env.USE_SCCACHE == 'true' }}
         shell: bash
         run: |
           set -euo pipefail
-          if [[ -n "${ACTIONS_CACHE_URL:-}" && -n "${ACTIONS_RUNTIME_TOKEN:-}" ]]; then
+          echo "ACTIONS_CACHE_URL set: $([[ -n "${ACTIONS_CACHE_URL:-}" ]] && echo yes || echo no)"
+          echo "ACTIONS_RESULTS_URL set: $([[ -n "${ACTIONS_RESULTS_URL:-}" ]] && echo yes || echo no)"
+          echo "ACTIONS_RUNTIME_TOKEN set: $([[ -n "${ACTIONS_RUNTIME_TOKEN:-}" ]] && echo yes || echo no)"
+          if [[ -n "${ACTIONS_RUNTIME_TOKEN:-}" && ( -n "${ACTIONS_CACHE_URL:-}" || -n "${ACTIONS_RESULTS_URL:-}" ) ]]; then
             echo "SCCACHE_GHA_ENABLED=true" >> "$GITHUB_ENV"
             echo "Using sccache GitHub backend"
           else