feat(windows): native ARM64 build (prebuilt PDFium/WebView2Loader + experimental workflow)

.github/workflows/windows-arm64.yml

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+name: Windows ARM64 (experimental)
+
+# Native Windows-on-ARM build, produced on GitHub's windows-11-arm runners
+# (free for public repositories). Kept as a standalone manually-triggered
+# workflow so it can be exercised and stabilised before being folded into
+# the release matrix. Remaining integration steps for release.yml are
+# listed in the PR description: user-mode variant, Authenticode signing
+# steps, and windows-aarch64 entries in the updater's latest.json.
+
+on:
+  workflow_dispatch:
+
+jobs:
+  build-windows-arm64:
+    runs-on: windows-11-arm
+    defaults:
+      run:
+        working-directory: open-pdf-studio
+    env:
+      TAURI_SIGNING_PRIVATE_KEY: ${{ secrets.TAURI_SIGNING_PRIVATE_KEY }}
+      TAURI_SIGNING_PRIVATE_KEY_PASSWORD: 'tauri2026'
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 20
+
+      - name: Install Rust stable (aarch64 host)
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Install frontend dependencies
+        run: npm install
+
+      - name: Select win-arm64 bundled resources
+        shell: pwsh
+        run: |
+          # tauri.windows.conf.json pins the x64 pdfium.dll and
+          # WebView2Loader.dll — and, as a platform override, Tauri merges it
+          # OVER tauri.conf.json, so the swap must happen HERE. Rewriting
+          # bundle.resources in the base tauri.conf.json is silently undone by
+          # this override and ships the x64 pdfium.dll in the arm64 bundle;
+          # init_pdfium can't load a wrong-arch DLL, PDFium stays uninitialised,
+          # and every page renders blank. Replace the whole resources object so
+          # the win-x64 key is dropped (no colliding pdfium.dll destination).
+          # (win-arm64 DLL provenance: src-tauri/binaries/win-arm64/README.md.)
+          $conf = Get-Content src-tauri/tauri.windows.conf.json -Raw | ConvertFrom-Json
+          $conf.bundle.resources = [ordered]@{
+            'binaries/win-arm64/pdfium.dll'         = 'pdfium.dll'
+            'binaries/win-arm64/WebView2Loader.dll' = 'WebView2Loader.dll'
+          }
+          $conf | ConvertTo-Json -Depth 10 | Set-Content src-tauri/tauri.windows.conf.json
+
+      # npm run tauri:build = prebuild hook (cargo build --release -p
+      # pdfium-worker) + vite build + tauri build. src-tauri/build.rs derives
+      # the sidecar's target-triple suffix from $TARGET, which is
+      # aarch64-pc-windows-msvc on these runners - no manual copy needed.
+      - name: Build Tauri app (native ARM64)
+        run: npm run tauri:build
+
+      - name: Verify installer architecture
+        shell: pwsh
+        working-directory: .
+        run: |
+          $setup = Get-ChildItem target/release/bundle/nsis/*-setup.exe | Select-Object -First 1
+          if (-not $setup) { Write-Error "No NSIS installer produced"; exit 1 }
+          Write-Output "Installer: $($setup.Name) ($([math]::Round($setup.Length/1MB,1)) MB)"
+          $bytes = [System.IO.File]::ReadAllBytes("target/release/open-pdf-studio.exe")
+          $peOffset = [BitConverter]::ToInt32($bytes, 0x3C)
+          $machine = [BitConverter]::ToUInt16($bytes, $peOffset + 4)
+          Write-Output ("PE machine type: 0x{0:X4}" -f $machine)
+          if ($machine -ne 0xAA64) { Write-Error "Main exe is not ARM64"; exit 1 }
+
+          # The bundled pdfium.dll must be ARM64 too. An x64 DLL here loads-fails
+          # at runtime, PDFium stays uninitialised, and pages render blank while
+          # the app otherwise runs — so the main-exe check above passes with
+          # rendering silently dead. Fail the build instead.
+          $dlls = Get-ChildItem -Path target/release -Recurse -Filter pdfium.dll -ErrorAction SilentlyContinue
+          if (-not $dlls) { Write-Warning "No bundled pdfium.dll found under target/release to verify" }
+          foreach ($dll in $dlls) {
+            $db = [System.IO.File]::ReadAllBytes($dll.FullName)
+            $dpe = [BitConverter]::ToInt32($db, 0x3C)
+            $dm = [BitConverter]::ToUInt16($db, $dpe + 4)
+            Write-Output ("pdfium.dll ($($dll.FullName)): 0x{0:X4}" -f $dm)
+            if ($dm -ne 0xAA64) { Write-Error "Bundled pdfium.dll is not ARM64"; exit 1 }
+          }
+
+      - name: Upload installer artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: open-pdf-studio-windows-arm64-setup
+          path: target/release/bundle/nsis/*-setup.exe
+          if-no-files-found: error
+          retention-days: 30

open-pdf-studio/src-tauri/binaries/win-arm64/LICENSE

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+Copyright 2014-2025 Benoit Blanchon
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+This package also includes third-party software. See the licenses/ directory for their respective licenses.

open-pdf-studio/src-tauri/binaries/win-arm64/README.md

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+# PDFium + WebView2Loader for Windows ARM64
+
+- `pdfium.dll`: PDFium prebuilt for win-arm64, from
+  https://github.com/bblanchon/pdfium-binaries/releases/tag/chromium%2F7834
+  (same chromium/7834 pin as the Linux fetch in `.github/workflows/release.yml`).
+  Licence: `LICENSE` in this directory (Apache-2.0/BSD-3-Clause, see file).
+- `WebView2Loader.dll`: win-arm64 native loader from the `Microsoft.Web.WebView2`
+  NuGet package, version 1.0.4078.44 (`runtimes/win-arm64/native/`).
+
+Selected at build time by the ARM64 workflow in
+`.github/workflows/windows-arm64.yml`, which rewrites `bundle.resources` to
+point here instead of `binaries/win-x64/`.