refactor: consolidate installer defaults and FILESYSTEM validation into config.sh

The installer had three sites touching FILESYSTEM: a top-level default in the monolith, a re-default block in gather_input, and a runtime validation block also in gather_input. The same scattering existed for LOCALE, KEYMAP, ENABLE_SSH, and NO_ENCRYPT. A future contributor changing one site wouldn't have known the other two existed.

Move all five defaults into the lib/config.sh declarations so config.sh is the single source of truth. Add validate_filesystem() in lib/config.sh and call it from main() between check_config and gather_input, so a typo in a config file's FILESYSTEM= fails fast before any install action runs.

The behavior change is stricter. An empty FILESYSTEM in a config file used to be silently defaulted to zfs, now it errors. Interactive mode is unaffected. select_filesystem still controls the value and already errored on cancellation.

Bats: 140 → 142. Five tests added in test_config.bats for the defaults pinning and validate_filesystem coverage. Three removed from test_archangel.bats for behavior that moved out of gather_input. Lint clean.

1 files changed, 19 insertions, 4 deletions

diff --git a/installer/lib/config.sh b/installer/lib/config.sh
index fefc838..65703d0 100644
--- a/installer/lib/config.sh
+++ b/installer/lib/config.sh
@@ -9,12 +9,18 @@
 CONFIG_FILE=""
 UNATTENDED=false
 
-# These get populated by config file or interactive prompts
-FILESYSTEM=""           # "zfs" or "btrfs"
+# These get populated by config file or interactive prompts.
+# Optional fields carry their default value here so config.sh is the
+# single source of truth — gather_input trusts what's loaded.
+FILESYSTEM="zfs"        # "zfs" or "btrfs"
+LOCALE="en_US.UTF-8"
+KEYMAP="us"
+ENABLE_SSH="yes"        # SSH with root login (default yes for headless)
+NO_ENCRYPT="no"         # Skip filesystem encryption (testing only)
+
+# Required fields — installer errors out if any are still empty at install time.
 HOSTNAME=""
 TIMEZONE=""
-LOCALE=""
-KEYMAP=""
 SELECTED_DISKS=()
 RAID_LEVEL=""
 WIFI_SSID=""
@@ -134,3 +140,12 @@ validate_config() {
     fi
     info "Config validation passed"
 }
+
+# Catches a typo in FILESYSTEM= from a config file before the install
+# starts. Called from main() after check_config so a bad value never
+# reaches gather_input or filesystem_preflight.
+validate_filesystem() {
+    if [[ "$FILESYSTEM" != "zfs" && "$FILESYSTEM" != "btrfs" ]]; then
+        error "Invalid FILESYSTEM: $FILESYSTEM (must be 'zfs' or 'btrfs')"
+    fi
+}