New crate implementing the application daemon entry point:
- crates/weft-appd/Cargo.toml: tokio (current-thread runtime), anyhow,
sd-notify, tracing dependencies
- crates/weft-appd/src/main.rs: async run() resolves IPC socket path
from WEFT_APPD_SOCKET or XDG_RUNTIME_DIR/weft/appd.sock; stubs for
AppRegistry, IpcServer, CompositorClient, RuntimeSupervisor,
CapabilityBroker, ResourceController per WEFT-OS-APPD-DESIGN.md;
sd_notify(READY=1) to be sent after IpcServer bind + CompositorClient
connect
- infra/systemd/weft-appd.service: Type=notify, Requires+After
weft-compositor.service, After servo-shell.service
Also fix two winit backend issues that were present in the working tree:
- remove spurious mut on display binding (never mutated after init)
- wrap std::env::set_var in unsafe block (required since Rust 1.80)
