fix(build): bundle both macOS architectures of esbuild's native binary

[devrosx]

Closes #462

Problem

esbuild ships its native binary via optionalDependencies (@esbuild/darwin-x64, @esbuild/darwin-arm64, …) — npm only installs the one matching the build host's architecture. The published x64 SuperCmd DMG is built on an Apple Silicon machine, so node_modules/@esbuild/ contains only darwin-arm64. electron-builder packs that same node_modules/ into both DMGs, so the x64 DMG ships an arm64 binary that it can't execute.

Every extension whose on-demand build invokes esbuild then fails on Intel/Rosetta Macs with the misleading message:

You installed esbuild for another platform than the one you're currently using.
…
Specifically the "@esbuild/darwin-arm64" package is present but this platform
needs the "@esbuild/darwin-x64" package instead.

The same problem exists for the nested esbuild copy under @raycast/api (a different version: 0.25.12 vs the top-level 0.19.12).

Confirmed by inspecting a packaged 1.0.25 build:

$ file SuperCmd.app/Contents/MacOS/SuperCmd
… Mach-O 64-bit executable x86_64

$ ls app.asar.unpacked/node_modules/@esbuild
darwin-arm64

$ ls app.asar.unpacked/node_modules/@raycast/api/node_modules/@esbuild
darwin-arm64

Fix

Two-part, both small:

1. Pin both platform packages explicitly in package.json so npm always installs them for the top-level esbuild regardless of the build host:

   "@esbuild/darwin-arm64": "0.19.12",
   "@esbuild/darwin-x64": "0.19.12",

2. Add scripts/ensure-cross-arch-esbuild.mjs (run from postinstall) which walks every esbuild folder it finds in node_modules (handles nested copies like @raycast/api/node_modules/esbuild at their own version) and npm packs the missing @esbuild/darwin-* sibling at the matching version. Idempotent, runs only on macOS, no-op when nothing is missing.

The script handles future esbuild version drift (e.g. when @raycast/api bumps its esbuild dependency) without needing a corresponding package.json change.

Verification

Reproduced the original failure with SuperCmd 1.0.25 on macOS 13.6 x86_64 (issue #462).

Local smoke test of the script:

# top-level esbuild 0.19.12 + nested @raycast/api/node_modules/esbuild 0.25.12,
# host arch x64 → only darwin-x64 installed.

$ node scripts/ensure-cross-arch-esbuild.mjs
  → installing @esbuild/darwin-arm64@0.25.12 for …/@raycast/api/node_modules/esbuild
  → installing @esbuild/darwin-arm64@0.19.12 for …/node_modules/esbuild
ensure-cross-arch-esbuild: added 2 missing platform package(s).

$ file node_modules/@esbuild/darwin-x64/bin/esbuild
… Mach-O 64-bit executable x86_64
$ file node_modules/@esbuild/darwin-arm64/bin/esbuild
… Mach-O 64-bit executable arm64

# re-run is a no-op:
$ node scripts/ensure-cross-arch-esbuild.mjs
ensure-cross-arch-esbuild: all esbuild instances already have both macOS binaries.

Alternatives considered

• Build x64 and arm64 in separate CI jobs (Intel + Apple Silicon runners). Cleanest but doubles CI cost and requires CI changes; this PR is contained to two files and doesn't touch the release pipeline.
• Bumping the top-level esbuild to ^0.25.x to deduplicate with @raycast/api's copy. Reduces the number of esbuild instances but is a larger functional change and doesn't itself fix the cross-arch problem.