fix: revert read-raw-byte poll check (unix-read must block)

The earlier fix that checked unix-simple-poll before unix-read
broke input: poll on fd 0 always returns NIL in this SBCL, so
read-raw-byte always returned nil. Reverted to original: call
unix-simple-poll (for timeout) then unix-read unconditionally.
unix-read blocks until data arrives, which is correct for a TUI.

src/components/input.lisp

@@ -75,11 +75,9 @@
     (sb-sys:with-pinned-objects (buf)
       (let ((sap (sb-sys:vector-sap buf)))
         (if timeout-ms
-            ;; Poll first: only read if data is ready
-            (if (sb-unix:unix-simple-poll fd :input timeout-ms)
+            (progn (sb-unix:unix-simple-poll fd :input timeout-ms)
                    (let ((n (sb-unix:unix-read fd sap 1)))
-                  (if (= n 1) (aref buf 0) (values nil :eof)))
-                nil)
+                     (if (= n 1) (aref buf 0) (values nil :eof))))
             (let ((n (sb-unix:unix-read fd sap 1)))
               (if (= n 1) (aref buf 0) (values nil :eof))))))))