fix: treat EPERM from kill(pid, 0) as "process exists" in daemon liveness checks (#564)

Per POSIX, kill(pid, 0) returns EPERM when the process exists but the
caller lacks permission to signal it, and ESRCH when it does not exist.
The daemon liveness checks in both the Rust CLI and TypeScript daemon
treated any kill failure as "not running", which is incorrect when
running inside a macOS sandbox that restricts signal delivery to
(target self). This caused the CLI to delete the real daemon's socket
and PID files, then spawn a duplicate daemon.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

cli/src/connection.rs

@@ -159,7 +159,13 @@ fn is_daemon_running(session: &str) -> bool {
     if let Ok(pid_str) = fs::read_to_string(&pid_path) {
         if let Ok(pid) = pid_str.trim().parse::<i32>() {
             unsafe {
-                return libc::kill(pid, 0) == 0;
+                if libc::kill(pid, 0) == 0 {
+                    return true;
+                }
+                // EPERM means the process exists but we lack permission to
+                // signal it (e.g. inside a macOS sandbox). Only ESRCH means
+                // the process is genuinely gone.
+                return std::io::Error::last_os_error().raw_os_error() != Some(libc::ESRCH);
             }
         }
     }