Stop the modem crash loop, and record what it is not

Fedora runs rmtfs with -r, which starts the modem remoteproc at boot. Since
the modem never gets past RF init, every C630 sits in a fatal crash and
recovery cycle every ~3.4 seconds from boot onwards — and is already a dozen
crashes deep by the time anyone logs in, which quietly confuses any manual
experiment. Drop the -r so the modem stays offline until asked for.

Also record today's eliminations, each of which closes an avenue: both
published _nm firmware builds are rejected by the boot ROM, not just the
newest; the PEP tables in this machine's own ACPI show Windows gives the
modem seven clocks, one 752 mV rail vote, cx/mx and IPA bandwidth, and
nothing whatsoever for RF — so the host does not power the RF front end on
either OS, and the one clock mainline lacks changes nothing when forced on;
and kernel bracketing is stuck, because 5.10 will not boot here at all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011XgGF5wfxLDAybVnNz6eNQ

overlay/etc/systemd/system/rmtfs.service.d/50-no-remoteproc.conf

@@ -0,0 +1,15 @@
+# Fedora runs rmtfs with -r, which makes it start the modem remoteproc at boot.
+# On this machine the modem cannot get past RF init (see docs/firmware.md), so
+# that means a fatal crash and recovery cycle every ~3.4 seconds, forever: log
+# spam, wasted power, and a wedged remoteproc if anything else pokes it.
+#
+# Drop -r so the modem stays offline until someone asks for it:
+#
+#     echo start | sudo tee /sys/class/remoteproc/remoteprocN/state
+#
+# (N varies between boots — find it by matching 4080000.remoteproc in
+# /sys/class/remoteproc/*/name.) Delete this file to restore the auto-start
+# once the modem is fixed.
+[Service]
+ExecStart=
+ExecStart=/usr/bin/rmtfs -P -s