ci: add vcpkg binary caching to Windows and macOS workflows

.github/workflows/build-macos.yml

@@ -69,6 +69,22 @@ jobs:
         with:
           vcpkgGitCommitId: 'ffc071e0c08432c60c9b64f00334c0227667931b'
 
+      - name: Restore vcpkg binary cache
+        id: vcpkg_cache
+        uses: actions/cache/restore@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: vcpkg-bincache-${{ runner.os }}-arm64-${{ hashFiles('vcpkg.json', 'vcpkg-lock.json') }}
+          restore-keys: |
+            vcpkg-bincache-${{ runner.os }}-arm64-
+
+      - name: Configure vcpkg cache directory
+        run: |
+          cacheDir="${{ github.workspace }}/vcpkg-bincache"
+          mkdir -p "$cacheDir"
+          echo "VCPKG_DEFAULT_BINARY_CACHE=$cacheDir" >> "$GITHUB_ENV"
+          echo "VCPKG_BINARY_SOURCES=clear;files,$cacheDir,readwrite" >> "$GITHUB_ENV"
+
       - name: Install Dependencies
         run: |
           export HOMEBREW_NO_REQUIRE_TAP_TRUST=1
@@ -349,6 +365,13 @@ jobs:
           CONFIG_STATUS=${PIPESTATUS[0]}
           if [ $CONFIG_STATUS -eq 0 ]; then echo "✅ CMake configuration complete"; else echo "❌ CMake configuration failed"; exit 1; fi
 
+      - name: Save vcpkg binary cache
+        if: ${{ steps.vcpkg_cache.outputs.cache-hit != 'true' && matrix.game.id == 'generalsxzh' }}
+        uses: actions/cache/save@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: ${{ steps.vcpkg_cache.outputs.cache-primary-key || format('vcpkg-bincache-{0}-arm64-{1}', runner.os, hashFiles('vcpkg.json', 'vcpkg-lock.json')) }}
+
       - name: Build ${{ matrix.game.value }}
         run: |
           mkdir -p logs

.github/workflows/build-windows.yml

@@ -57,6 +57,25 @@ jobs:
         with:
           arch: x86
 
+      - name: Restore vcpkg binary cache
+        id: vcpkg_cache
+        uses: actions/cache/restore@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: vcpkg-bincache-${{ runner.os }}-x86-${{ hashFiles('vcpkg.json', 'vcpkg-lock.json') }}
+          restore-keys: |
+            vcpkg-bincache-${{ runner.os }}-x86-
+
+      - name: Configure vcpkg cache directory
+        shell: pwsh
+        run: |
+          $cacheDir = "${{ github.workspace }}/vcpkg-bincache"
+          New-Item -ItemType Directory -Force -Path $cacheDir | Out-Null
+          "VCPKG_DEFAULT_BINARY_CACHE=$cacheDir" >> $env:GITHUB_ENV
+          "VCPKG_BINARY_SOURCES=clear;files,$cacheDir,readwrite" >> $env:GITHUB_ENV
+          "VCPKG_OVERLAY_TRIPLETS=${{ github.workspace }}/triplets" >> $env:GITHUB_ENV
+          "VCPKG_INSTALL_OPTIONS=--x-abi-tools-use-exact-versions" >> $env:GITHUB_ENV
+
       - name: Configure
         shell: pwsh
         run: |
@@ -71,6 +90,13 @@ jobs:
             -DSAGE_USE_DX8=ON `
             -DSAGE_USE_DETERMINISTIC_MATH=ON
 
+      - name: Save vcpkg binary cache
+        if: ${{ steps.vcpkg_cache.outputs.cache-hit != 'true' && matrix.game.id == 'generalsxzh' }}
+        uses: actions/cache/save@v4
+        with:
+          path: ${{ github.workspace }}/vcpkg-bincache
+          key: ${{ steps.vcpkg_cache.outputs.cache-primary-key || format('vcpkg-bincache-{0}-x86-{1}', runner.os, hashFiles('vcpkg.json', 'vcpkg-lock.json')) }}
+
       - name: Build
         shell: pwsh
         run: cmake --build --preset win32-vcpkg --target ${{ matrix.game.target }}

docs/WORKLOG/2026-09-DIARY.md

@@ -27,6 +27,11 @@
   - `.github/prompts/review-pull-request.prompt.md`: Focused on architectural coherence, merge safety, platform isolation, determinism, improvement opportunities, edge cases, and 1-commit policy enforcement, with an interactive inquiry allowing the user to trigger CodeRabbit triage.
   - `.github/prompts/resolve-coderabbit-findings.prompt.md`: Dedicated prompt to triage, address, or technically rebut all CodeRabbit review findings via GitHub API without conversational filler, preserving dual-engine parity and deterministic math.
 
+### Cross-Platform CI Build Caching
+- Introduced vcpkg binary caching (`actions/cache/restore` and `actions/cache/save`) on Windows MSVC (`x86-windows`) in `.github/workflows/build-windows.yml` to prevent rebuilding dependencies from source and dramatically reduce CI duration.
+- Added parity vcpkg binary caching for macOS (`arm64-osx`) in `.github/workflows/build-macos.yml`.
+- Configured dedicated cache key hashing on both `vcpkg.json` and `vcpkg-lock.json` alongside fallback prefix restore keys.
+
 ## 06/09/2026
 ### Abort Premature SCUD Storm Launches
 - Fixed issue #284 by making the existing missile-launcher null guard active in normal builds and safely checking the special-power lookup.