feat(day0): promote expand_root_lv to a canonical day0 step

The half-disk LV pattern affects ~90% of mk-labs VMs. Treating the
fix-up as application-specific (as it was in day1_deploy_honcho.yml)
means future deploys would each carry the same boilerplate, and any
day1 author could forget it.

This commit:

  * Adds playbooks/day0_expand_root_lv.yml — standalone day0 step,
    targets {{ target | default("all") }}, honors a per-host
    expand_root_lv_skip opt-out for multi-LV layouts.

  * Adds playbooks/day0_provision.yml — umbrella playbook chaining
    day0_linux_baseline + day0_expand_root_lv, so the operator runs
    ONE command per new VM.

  * Removes expand_root_lv from day1_deploy_honcho.yml — day0 is
    assumed complete before day1 begins (cleaner separation of
    concerns, matches the convention day1_deploy_semaphore already
    follows).

  * Updates the role README to document the lifecycle position and
    the opt-out flag for hosts with multi-LV plans.

ansible/playbooks/day0_provision.yml

@@ -0,0 +1,30 @@
+---
+# ============================================================================
+# day0_provision.yml
+# ----------------------------------------------------------------------------
+# Umbrella day0 playbook. Runs the full host-provisioning lifecycle in
+# the correct order against newly-built VMs, so the operator runs ONE
+# command per new host rather than chaining day0 steps manually.
+#
+# Order matters:
+#   1. linux-baseline      — timezone, NTP, packages, SSH hardening, jarvis user
+#   2. expand_root_lv      — reclaim PE left unallocated by the Ubuntu
+#                            autoinstall template default
+#
+# Idempotent: every step is safe to re-run. Suitable to apply periodically
+# from Semaphore as a baseline-drift check.
+#
+# Usage:
+#   ansible-playbook playbooks/day0_provision.yml -e target=lincoln
+#   ansible-playbook playbooks/day0_provision.yml -e target=honcho_server
+#
+# For finer control over a single phase, the constituent playbooks are:
+#   playbooks/day0_linux_baseline.yml
+#   playbooks/day0_expand_root_lv.yml
+# ============================================================================
+
+- name: Import day0 linux baseline
+  ansible.builtin.import_playbook: day0_linux_baseline.yml
+
+- name: Import day0 expand root LV
+  ansible.builtin.import_playbook: day0_expand_root_lv.yml