fix(ci): cross-compile macOS x64 desktop build on Apple Silicon runner

[bborn]

Problem

GitHub retired the Intel macos-13 runner image. The macos-x64 bundle job in desktop.yml now queues forever — yesterday's run (27376820607) has had it stuck in queued for ~19h while macos-arm64 and linux-x64 completed. Net effect: v0.3.8 has no Intel DMG (TaskYou-macos-x64.dmg 404s), which also blocks the Intel path of the new install-macos.sh (#595).

Fix

Cross-compile the x64 bundle on an Apple Silicon runner:

• macos-x64 matrix entry moves macos-13 → macos-14
• dtolnay/rust-toolchain gets targets: ${{ matrix.triple }} so x86_64-apple-darwin is installed (tauri build already passes --target)
• the ty sidecar builds with a new per-entry goarch matrix value (GOARCH=amd64 for the cross entry; native values elsewhere, so arm64/linux builds are unchanged)

Cross-arch Go auto-disables CGO, which is safe here: the sqlite driver is pure Go (modernc.org/sqlite).

Verification

• GOARCH=amd64 go build ./cmd/task on an arm64 Mac → Mach-O 64-bit executable x86_64 ✅
• Real proof needs a workflow_dispatch run of Desktop after merge — that will also backfill the missing x64 assets (re-tag or dispatch + gh release upload for v0.3.8).

🤖 Generated with Claude Code

[bborn]

QA evidence — real workflow_dispatch run on this branch

Dispatched the Desktop workflow on fix/desktop-x64-cross-compile: run 27424261234. All three jobs green — Bundle (macos-x64) completed in 5m13s on the Apple Silicon runner, vs. queued-forever on the retired macos-13 image (yesterday's run had it stuck in queued for 19+ hours).

Artifact verification (cross-compile produced real x86_64 binaries)

Downloaded the taskyou-desktop-macos-x64 artifact from the run, mounted the DMG:

$ file TaskYou.app/Contents/MacOS/*
TaskYou.app/Contents/MacOS/taskyou-desktop: Mach-O 64-bit executable x86_64
TaskYou.app/Contents/MacOS/ty:              Mach-O 64-bit executable x86_64

Both the Tauri shell and the Go ty sidecar are genuine x86_64 (DMG: 15 MB). Since this was a workflow_dispatch (not a tag), the attach-to-release step was skipped by design — after merge, a dispatch + gh release upload v0.3.8 --clobber from the artifacts backfills the missing Intel asset.

🤖 Generated with Claude Code