fix: negative line length, write(2) to bad fd

client.s

@@ -92,15 +92,17 @@ client__pollout:
     mov rbx, rdx
     mov r12, rsi
 
+    push rdi
     mov rdi, r12
+    add rdi, OFFSET_CLIENT_BUFFER
     mov rsi, 255
     call scanline
+    pop rdi
 
     ; poll(2)'d for POLLOUT but we had no line buffered;
     ; should be impossible
     cmp rax, 0
-    mov rax, -1024
-    je client__pollout__return
+    je client__pollout__no_line
 
     mov r13, rax
 
@@ -135,6 +137,9 @@ client__pollout__shunt__finished:
     jl client__pollout__return
     mov word [pollfds + rbx * pollfd_size + 4], POLLIN
 
+client__pollout__no_line:
+    mov rax, -1024
+
 client__pollout__return:
     pop r13
     pop r12