fix: reduce desktop installer size

[hrhrng]

What changed

• publish separate Apple Silicon and Intel macOS installers instead of making the universal DMG the default
• prune opposite-architecture Claude Agent SDK, Remotion compositor, and esbuild binaries after packaging
• keep the Remotion bundler and Studio toolchain out of the production app while retaining the prebuilt render bundle
• expose both macOS downloads on the desktop-first download page
• update CI and rolling preview release assets for both architectures

Why

The universal package bundled two Electron architectures and both copies of large native agent/render runtimes. Even an arm64 build retained x64 native packages, and the production dependency graph also pulled in the development-only Remotion Studio/bundler stack.

Impact

The verified Apple Silicon DMG drops from 463,342,810 bytes to 262,852,091 bytes (43.3% smaller). The Intel DMG is 267,799,867 bytes. Each package keeps only its native runtime.

Validation

• desktop tests: 92 passed
• web tests: 43 passed
• desktop and web type checks passed
• full workspace lint passed
• both workflow YAML files parsed successfully
• arm64 and x64 DMGs built locally and passed hdiutil verify
• packaged executable architectures and native runtime pruning verified
• packaged icon hash matches the restored Clash agent logo source