init: add dormant driver-manager service files (C0)

Adds the two dormant service files for the driver-manager
post-switchroot + initfs spawner paths. Both files are dormant by
default — they require /etc/driver-manager.d/{disabled,initfs-active}
to be absent before they activate. The cutover (C1-C4) is
operator-ratified; this commit only adds the file presence so
the C0 wiring exists.

Refs: local/docs/DRIVER-MANAGER-MIGRATION-PLAN.md § 5.2 C0.

init.d/00_driver-manager.service

@@ -0,0 +1,26 @@
+# Place this file at:
+#   local/sources/base/init.d/00_driver-manager.service
+# (created during D5/C0 phase; remains dormant until operator ratifies cutover)
+
+[unit]
+description = "Driver manager (post-switchroot /usr spawner)"
+# Long-form description:
+#   Driver manager enumerates /scheme/pci, reads /lib/drivers.d/*.toml,
+#   matches devices against driver match tables, and spawns driver daemons
+#   (e1000d, xhcid, ihdgd, etc.) per the manager's SpawnDecision committee
+#   (see § 5.1 D1 migration plan). Activates only when
+#   ConditionPathExists for /etc/driver-manager.d/disabled fails AND all
+#   depends_on schemes (pci, firmware, iommu, numad, etc.) are ready.
+#
+# Until the D5 feature-complete gate ratifies, this service is dormant —
+# pcid-spawner retains the boot path. The dormant flag is enabled by
+# default; C0 wiring must explicitly remove it before activation.
+
+[service]
+cmd = "driver-manager"
+args = ["--rootfs"]
+# oneshot so a hypothetical bind handle error doesn't loop the manager
+type = "oneshot_async"
+# Operator must explicitly enable this service:
+#   touch /etc/driver-manager.d/disabled  # force fallback to pcid-spawner
+ConditionPathExists = "/etc/driver-manager.d/disabled"

init.initfs.d/40_driver-manager-initfs.service

@@ -0,0 +1,21 @@
+# Place this file at:
+#   local/sources/base/init.initfs.d/40_driver-manager-initfs.service
+# (created during D5/C0 phase; remains dormant until operator ratifies cutover)
+
+[unit]
+description = "Driver manager initfs spawner"
+requires_weak = ["10_inputd.service", "20_graphics.target", "40_pcid.service"]
+# Long-form description:
+#   Driver manager initfs variant. Replaces 40_pcid-spawner-initfs.service
+#   once the initfs storage path is fully verified under driver-manager
+#   in dual-mode observation (C1). Storage-critical drivers (ahcid, ided,
+#   nvmed, virtio-blkd) bind here before redoxfs mounts the rootfs.
+
+[service]
+cmd = "driver-manager"
+args = ["--initfs"]
+type = "oneshot"
+# Operator must explicitly enable this service by removing the
+# ConditionPathExists flag (C2 wiring). Until then, pcid-spawner
+# initfs continues to operate.
+ConditionPathExists = "/etc/driver-manager.d/initfs-active"