[hyzyla]

Linux releases currently provide only an ARM64 package. Add a linux-x64 package so x86_64 Ubuntu hosts can build ARM64 iPhone apps using the same Linux engine. Device destinations select ARM64 independently of the compiler host.

This includes the SDK export, Ubuntu import/setup, and Linux doctor commands needed to prepare either host. Setup pins the compiler and driver dependencies, verifies host-specific tool downloads, and detects SDK tools for the wrong host. The supporting fixes cover Linux build/install/clean routing, scheme build/archive shell actions, device discovery/timeouts, and package upgrades.

CI builds and checks both Linux packages on hosted x64 and ARM64 Ubuntu runners for relevant PRs and main pushes. Each job checks installation in a clean container. SDK-dependent app checks stay manual and are excluded from this PR’s CI gate because no private SDK runners are registered. The macOS hot-reload check uses an isolated simulator with bounded boot and cleanup, matching the smoke test’s isolation.

Validation:

• All 10 hosted PR checks passed, including x64/ARM64 packages, clean Ubuntu installs, and macOS regression tests. The macOS CLI e2e needed one retry after a log-stream shutdown timeout.
• 2,126 Rust tests and 53 Linux Python tests passed; clippy, formatting, documentation build, and TypeScript passed.
• Both package architectures passed clean-install and wrong-host rejection checks.
• A complete fresh x64 Ubuntu bootstrap downloaded and PGP-verified Swift, verified xtool, imported a new SDK without reuse, and compiled Swift Build and macros from cold sources.
• Doctor reported zero required problems; repeated setup preserved the driver and SDK. Independent ARM64 iPhone and simulator builds passed with zero warnings/errors using the normal Dash/Bubblewrap path.
• Workflow syntax and expressions passed actionlint. Private SDK/signing data are excluded from public packages and CI artifacts.

The x64 release assets are prepared for the next CLI release; this PR does not publish a release. .omo and optional dependency cleanup remain deferred.

Closes #349.