fix(release): add the cross-compile target to the pinned toolchain, not stable

[filipeforattini]

Follow-up to #244. The v0.65.0 release shipped Linux x86_64/aarch64, macOS aarch64 and Windows x86_64 — the optional + verify-assets design did its job — but the new macOS Intel leg failed, as flagged.

The failure

failed to build app: Target x86_64-apple-darwin is not installed
  (installed targets: aarch64-apple-darwin)

…even though dtolnay/rust-toolchain ran with targets: x86_64-apple-darwin and exited 0. The log confirms it executed:

rustup toolchain install stable --target x86_64-apple-darwin --profile minimal --no-self-update
  stable-aarch64-apple-darwin updated - rustc 1.97.1

apps/desktop/src-tauri/rust-toolchain.toml pins channel = "1.95.0", and rustup's directory override wins inside that directory. So the target landed on stable (1.97.1) while the build ran under 1.95.0 — and the error's "installed targets" list is 1.95.0's, not stable's.

Native legs never surfaced this, because a toolchain always has its own host target. Only a cross-compile can notice.

Reproduced locally:

$ rustup show active-toolchain            # repo root
stable-x86_64-unknown-linux-gnu (default)
$ cd apps/desktop/src-tauri && rustup show active-toolchain
1.95.0-x86_64-unknown-linux-gnu (overridden by '.../rust-toolchain.toml')

Fix: add the target by running rustup target add with working-directory: apps/desktop/src-tauri, so it lands on the toolchain that actually builds.

Also, from ../dit

Arch detection was wrong — $env:PROCESSOR_ARCHITECTURE describes the process, not the machine. On Windows on ARM an emulated x64 PowerShell reports AMD64, so an arm64 host looked like a plain x64 one and never got the emulation note. Now uses RuntimeInformation::OSArchitecture, like dit's installer.

Worth noting: OSArchitecture spells it X64, not AMD64 — verified live in a pwsh container. A naive swap would have sent every x64 machine down the default branch and hard-failed the installer. The match accepts both spellings, and all branches are exercised.

Docs: dit's & ([scriptblock]::Create((irm ...))) -Version ... form passes parameters in one line. Replaces my "download the script first" instruction, since iex takes no parameters — verified the scriptblock actually binds -Version/-Force.

Verification

• install.ps1 parses under pwsh 7.4; full flow re-run against the live v0.65.0 release: tag resolves, real .exe downloads, sha256 verifies, tampered file rejected
• Arch branch table checked against the values OSArchitecture really emits (X64/Arm64/X86/ARM)
• Prettier clean

The macOS Intel leg stays optional until it goes green once in a real release.

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