mount: use bcachefs -o X-mount.subdir={name} for subvolume mounts; update SAFETY notes; sync README and PROMPT with root/subvol scheme and bcachefs option

src/orchestrator/run.rs

@@ -201,7 +201,10 @@ pub fn run(ctx: &Context) -> Result<()> {
         let fs_results = zfs::make_filesystems(&fs_plan)?;
         info!("orchestrator: created {} filesystem(s)", fs_results.len());
 
-        // Next steps (mounts, optional fstab, state report) will be wired in follow-ups.
+        // Mount planning and application
+        let mplan = crate::mount::plan_mounts(&fs_results, &ctx.cfg)?;
+        let mres = crate::mount::apply_mounts(&mplan)?;
+        crate::mount::maybe_write_fstab(&mres, &ctx.cfg)?;
         return Ok(());
     }