samba: deadtime=0 (was 5) so WIM-apply idle does not drop the staging mount

WinPE maps the enrollment share early, then idles for minutes while the WIM
applies. deadtime=5 dropped that idle session, so the post-apply staging
copies failed (bay left with only site-config.json staged). VM test against
the live share copied everything fine on a fresh mount; the only difference
was the idle. deadtime=0 disables idle auto-disconnect. Applied live to the
current box (smbd reloaded); this makes it permanent + covers the second box
on the next playbook run.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

playbook/pxe_server_setup.yml

@@ -571,7 +571,11 @@
           # the short-lived flows that PXE imaging produces.
              socket options = TCP_NODELAY SO_KEEPALIVE IPTOS_LOWDELAY
              keepalive = 30
-             deadtime = 5
+             # deadtime=0 (disabled): WinPE maps the enrollment share early then
+             # idles for minutes during the WIM apply. A non-zero deadtime drops
+             # that idle session, so the post-apply staging copies failed (bay
+             # left with only site-config.json). 0 = never auto-disconnect idle.
+             deadtime = 0
 
     - name: "Configure Samba shares"
       blockinfile: