Phase 1.4: Add filesystem selection prompt

- Add FILESYSTEM variable to config (zfs or btrfs)
- Add select_filesystem() function with fzf support
- Update gather_input() to prompt for filesystem in interactive mode
- Add validation for FILESYSTEM in unattended mode
- Btrfs selection errors with "not yet implemented"
- Update banner to show "Archangel" branding
- Update config example with FILESYSTEM option

Groundwork for btrfs support - filesystem choice is now captured,
installation logic gates on FILESYSTEM variable.

1 files changed, 32 insertions, 0 deletions

diff --git a/custom/lib/common.sh b/custom/lib/common.sh
index 2f8844e..c271aec 100644
--- a/custom/lib/common.sh
+++ b/custom/lib/common.sh
@@ -101,6 +101,38 @@ fzf_multi() {
 }
 
 #############################
+# Filesystem Selection
+#############################
+
+# Select filesystem type (ZFS or Btrfs)
+# Sets global FILESYSTEM variable
+select_filesystem() {
+    step "Select Filesystem"
+
+    local options=(
+        "ZFS - Native encryption, best data integrity (recommended)"
+        "Btrfs - Native Linux, GRUB snapshot boot"
+    )
+
+    local selected
+    selected=$(fzf_select "Filesystem:" "${options[@]}")
+
+    case "$selected" in
+        ZFS*)
+            FILESYSTEM="zfs"
+            info "Selected: ZFS"
+            ;;
+        Btrfs*)
+            FILESYSTEM="btrfs"
+            info "Selected: Btrfs"
+            ;;
+        *)
+            error "No filesystem selected"
+            ;;
+    esac
+}
+
+#############################
 # Disk Utilities
 #############################