The casement crate was depended on through a sibling-repo path
(`../../../winit`) that only existed on the maintainer's machine,
so CI couldn't load the workspace manifest and every Rust Check
job died with "failed to read winit/Cargo.toml".
Vendoring it as a real submodule under `vendor/casement` (matching
the `vendor/jian` pattern, picked up by CI's `submodules:
recursive` checkout) closes that gap. The renamed GitHub repo
`ZSeven-W/casement` (was `ZSeven-W/winit`) tracks the `op-file-open`
branch — `feat(macos): drain_opened_file_urls` + the package rename
landed there as commit 5877fa83.
- `.gitmodules`: add vendor/casement.
- Root Cargo.toml: exclude vendor/casement from the workspace glob
(it's its own workspace).
- op-host-native + op-host-desktop: path = "../../vendor/casement".
25e644dbc7