fix(release): stage desktop dependencies per architecture

[AprilNEA]

Summary

• materialize one production staging directory per target CPU with pnpm deploy --cpu=<arch>
• package x64 and ARM64 separately so each artifact carries only its matching napi-rs keyring binding
• merge the separately generated macOS/Windows updater manifests while retaining x64 as the legacy fallback entry
• keep Linux updater manifests architecture-specific

Root cause

The desktop release cross-packs x64 and ARM64 artifacts on one runner, while pnpm previously installed only the runner CPU's @napi-rs/keyring-* optional package. The opposite-architecture artifact therefore lacked its keyring binding, and all three v0.13.0 packaging jobs failed artifact verification.

Without that verification, affected builds would silently fall back to plaintext daemon credential storage.

Verification

• x64 pnpm deploy --cpu=x64 staging contains only the Darwin x64 keyring binding
• ARM64 pnpm deploy --cpu=arm64 staging contains only the Darwin ARM64 keyring binding
• updater manifest merge regression test
• pnpm check:ci
• pnpm test — 2235 passed, 1 skipped
• Build Desktop run 30624768061 — macOS, Windows, and Linux packaging, artifact verification, and uploads passed

Linear: CODE-516

[linear-code]

CODE-516