Phase 6: replace rm+rename with rsync --delete pend/ prev/

lib/commands/run.js

@@ -1,7 +1,7 @@
 /**
  * run command — full backup run.
  */
-import { mkdir, rename, writeFile } from 'fs/promises';
+import { mkdir, writeFile } from 'fs/promises';
 import { join } from 'path';
 import { run as spawn, capture } from '../spawn.js';
 import { parseItemize } from '../itemize.js';
@@ -132,14 +132,7 @@ export async function runCommand(config) {
   // ── Phase 6: Promote PEND → PREV ────────────────────────────
   await setPhase(deltas, state, PHASES.PROMOTING, dry);
   console.log('\n── Promote PEND → PREV ──');
-
-  if (!dry) {
-    await rm(prev, { recursive: true, force: true });
-    await rename(pend, prev);
-    console.log(`  ${pend} → ${prev}`);
-  } else {
-    console.log(`[dry-run] rm -rf ${prev} && mv ${pend} ${prev}`);
-  }
+  await spawn('rsync', ['-aP', '--delete', trailingSlash(pend), trailingSlash(prev)], { dryRun: dry });
 
   // ── Done ─────────────────────────────────────────────────────
   state.last_complete = seq;