apply mode: wire partition apply + mkfs; btrfs RAID1 flags and -f; UEFI detection and skip bios_boot when UEFI; sgdisk-based partition apply; update TODO and REGION markers

src/util/mod.rs

@@ -4,11 +4,13 @@
 // api: util::run_cmd(args: &[&str]) -> crate::Result<()>
 // api: util::run_cmd_capture(args: &[&str]) -> crate::Result<CmdOutput>
 // api: util::udev_settle(timeout_ms: u64) -> crate::Result<()>
+// api: util::is_efi_boot() -> bool
 // REGION: API-END
 //
 // REGION: RESPONSIBILITIES
 // - Centralize external tool discovery and invocation (sgdisk, blkid, mkfs.*, udevadm).
 // - Provide capture and error mapping to crate::Error consistently.
+// - Provide environment helpers (udev settle, boot mode detection).
 // Non-goals: business logic (planning/validation), direct parsing of complex outputs beyond what callers need.
 // REGION: RESPONSIBILITIES-END
 //
@@ -39,6 +41,7 @@
 
 use crate::{Error, Result};
 use std::process::Command;
+use std::path::Path;
 use tracing::{debug, warn};
 
 /// Captured output from an external tool invocation.
@@ -147,6 +150,14 @@ pub fn udev_settle(timeout_ms: u64) -> Result<()> {
     }
 }
 
+/// Detect whether the current system booted via UEFI (initramfs-friendly).
+///
+/// Returns true when /sys/firmware/efi exists (standard on UEFI boots).
+/// Returns false on legacy BIOS boots where that path is absent.
+pub fn is_efi_boot() -> bool {
+    Path::new("/sys/firmware/efi").exists()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;