fix: Alpine parliament Docker build (musl clean rebuild)

Ignore/clean host objects, add linux-headers, and include sys/time.h
so discover builds under musl. Docker chair↔member handshake now passes.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/discover.c

@@ -32,7 +32,9 @@ static void disc_close(disc_sock_t s) { closesocket(s); }
 #include <errno.h>
 #include <fcntl.h>
 #include <netinet/in.h>
+#include <sys/select.h>
 #include <sys/socket.h>
+#include <sys/time.h>
 #include <unistd.h>
 typedef int disc_sock_t;
 #define DISC_BAD (-1)