Migrate system presets to v2

System presets now use version = 2. Version 1 manifests are rejected before Shine runs detection, an installer, elevation, or profile writes. Existing ~/.shine/sys-manifest.toml run records remain readable; this migration changes preset authoring, not recorded software ownership.

For each init item, replace the platform-wide init.sh or init.ps1 dispatcher with both:

• a read-only detect declaration (command, path, or any); and
• an install declaration using a fixed package provider or one item-specific script under install/.

Set version = 2 at the manifest root. Move software-specific shell content into [[items.shell]] or an item-owned profile/<item>.* fragment. Base profile files may contain only platform-wide content. Remove status/update wire-protocol output and update-check dispatches: users upgrade third-party software with its package manager or upstream tool.

External install scripts, base profile files, fragments, eval, and source remain protected by the global allow_sys_code = true setting. Static detection, provider metadata, PATH, environment, and aliases do not need that permission. Start from shine preset copy sys/<os> and validate with:

shine sys list
shine sys info <ITEM>
shine sys bootstrap <ITEM> --dry-run