fix(desktop): allow clippy::print_stderr at terminal error path in main

WHY: `cargo clippy --workspace --all-targets -- -D warnings` (`just ci`)
flagged the bare `eprintln!` in `main.rs:30` introduced when the entry
point gained the runtime-init prelude. The terminal error path in a
binary is the correct place for stderr output before `process::exit(1)`
— same rationale as the CLI's file-level `#![allow(clippy::print_stderr)]`
in `crates/cli/src/main.rs`. Inline-scoped `#[allow]` is preferred here
because the rest of the file should not silently gain print_stderr
suppression.

CI was red on all 3 OS jobs of PR #167 with this lone clippy error.

Author: utof

crates/desktop/src/main.rs

@@ -27,7 +27,13 @@ fn main() {
     let _guard = runtime.enter();
 
     if let Err(err) = perima_desktop::run() {
-        eprintln!("perima-desktop exited with error: {err:#}");
+        // WHY allow(clippy::print_stderr): this is the terminal error path in a
+        // binary entry point — writing to stderr before exit is the correct UX.
+        // The CLI crate suppresses the same lint with the same rationale.
+        #[allow(clippy::print_stderr)]
+        {
+            eprintln!("perima-desktop exited with error: {err:#}");
+        }
         std::process::exit(1);
     }
 }