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/cli/args.rs

@@ -113,6 +113,10 @@ pub struct Cli {
     /// Write detection/planning JSON report to the given path (overrides config.report.path)
     #[arg(long = "report")]
     pub report: Option<String>,
+
+    /// Execute destructive actions (apply mode). When false, runs preview-only.
+    #[arg(long = "apply", default_value_t = false)]
+    pub apply: bool,
 }
 
 /// Parse CLI arguments (non-interactive; suitable for initramfs).