Add Windows ARM64 build support (#834)

* feat(build): add Windows ARM64 build support

- .goreleaser.yml
- .github/workflows/release.yml
- winget/SteveYegge.beads.installer.yaml

Add Windows ARM64 (aarch64) build target to support modern Windows devices
like Surface Pro X and Snapdragon-based laptops.

Changes:
- Added bd-windows-arm64 build configuration with CGO cross-compiler
- Installed gcc-mingw-w64-aarch64 toolchain in CI release workflow
- Added ARM64 installer entry to WinGet manifest (placeholder SHA256)
- Updated release header to mention Windows ARM64 support

The npm package already supports ARM64 in its cpu array.

Fixes: #833

* fix(build): use CGO_ENABLED=0 for Windows ARM64

- Remove non-existent gcc-mingw-w64-aarch64 package from CI
- Use CGO_ENABLED=0 since ncruces/go-sqlite3 is WASM-based
- Remove unnecessary CC/CXX cross-compiler settings

Addresses review feedback from @steveyegge on PR #834.

* style: remove inconsistent inline comment from goreleaser config

Aligns with existing style where CGO_ENABLED entries have no inline comments.

winget/SteveYegge.beads.installer.yaml

@@ -10,5 +10,8 @@ Installers:
   - Architecture: x64
     InstallerUrl: https://github.com/steveyegge/beads/releases/download/v0.30.7/beads_0.30.7_windows_amd64.zip
     InstallerSha256: 91A3D0799533DE8FA9AAB6415B8A57BDD542C59A21805FBF80A559A53F3CD02E
+  - Architecture: arm64
+    InstallerUrl: https://github.com/steveyegge/beads/releases/download/v0.30.7/beads_0.30.7_windows_arm64.zip
+    InstallerSha256: "0000000000000000000000000000000000000000000000000000000000000000"
 ManifestType: installer
 ManifestVersion: 1.6.0