feat(expand_root_lv): new role to grow root LV to fill VG + resize fs

Reclaims the half-disk LV left by the Ubuntu Server autoinstall
template default. Idempotent — no-ops cleanly when there are no free PE
in the VG, and exits the play cleanly on hosts without LVM.

Supports ext4 and xfs. Does not handle partition resize (cloud-utils
growpart) — out of scope for the template fix-up case.

Wired into day1_deploy_honcho.yml ahead of the honcho role so newly
provisioned VMs get the fix-up automatically. Suitable to add to any
day1 playbook by simply listing it before the application role.

ansible/roles/expand_root_lv/tasks/main.yml

@@ -0,0 +1,70 @@
+---
+# ============================================================================
+# expand-root-lv / main
+# ----------------------------------------------------------------------------
+# 1. Confirm the target VG exists (skip role cleanly on non-LVM hosts).
+# 2. Read free physical-extent count for the VG.
+# 3. Extend the LV to +100%FREE only when free_pe > 0.
+# 4. Grow the filesystem on the mountpoint (ext4 -> resize2fs, xfs -> xfs_growfs).
+# Each step is idempotent and skips when there's nothing to do.
+# ============================================================================
+
+- name: Gather LVM facts
+  ansible.builtin.command:
+    cmd: "vgs --noheadings --nosuffix --units b -o vg_name,vg_free_count {{ expand_root_lv_vg_name }}"
+  register: vg_info
+  changed_when: false
+  failed_when: false
+
+- name: Skip role when target VG is absent
+  ansible.builtin.meta: end_play
+  when: vg_info.rc != 0
+
+- name: Parse free PE count
+  ansible.builtin.set_fact:
+    expand_root_lv_free_pe: "{{ (vg_info.stdout.split() | last | int) if vg_info.stdout | length > 0 else 0 }}"
+
+- name: Extend LV to fill VG (only if free PE > 0)
+  ansible.builtin.command:
+    cmd: "lvextend -l +100%FREE /dev/{{ expand_root_lv_vg_name }}/{{ expand_root_lv_lv_name }}"
+  register: lvextend_result
+  when: expand_root_lv_free_pe | int > 0
+  changed_when: lvextend_result.rc == 0
+
+- name: Detect filesystem type at mountpoint
+  ansible.builtin.command:
+    cmd: "findmnt {{ expand_root_lv_mountpoint }} -no FSTYPE"
+  register: fstype_result
+  changed_when: false
+
+- name: Set filesystem type fact
+  ansible.builtin.set_fact:
+    expand_root_lv_fstype: "{{ fstype_result.stdout | trim }}"
+
+- name: Grow ext4 filesystem
+  ansible.builtin.command:
+    cmd: "resize2fs /dev/{{ expand_root_lv_vg_name }}/{{ expand_root_lv_lv_name }}"
+  register: resize_result
+  when:
+    - expand_root_lv_fstype == "ext4"
+    - lvextend_result.changed | default(false)
+  changed_when: resize_result.rc == 0
+
+- name: Grow xfs filesystem
+  ansible.builtin.command:
+    cmd: "xfs_growfs {{ expand_root_lv_mountpoint }}"
+  register: xfs_result
+  when:
+    - expand_root_lv_fstype == "xfs"
+    - lvextend_result.changed | default(false)
+  changed_when: xfs_result.rc == 0
+
+- name: Report current root size
+  ansible.builtin.command:
+    cmd: "df -h {{ expand_root_lv_mountpoint }}"
+  register: df_result
+  changed_when: false
+
+- name: Show post-resize disk usage
+  ansible.builtin.debug:
+    msg: "{{ df_result.stdout_lines }}"