fix(newos4): print the checkpoint name actually saved (auto)

Task 2 + ship of plan 2026-10-27_061724-newos4-checkpoint-name-mismatch.md.

module-system.js `checkpoint` read the clock a second time for the printed
name, so the name in "✅ Checkpoint created: <name>" differed from the name on
disk by >=1ms whenever no explicit name was given. It now prints the value
returned by fs.checkpoint(). try/catch and error strings unchanged.

Bundles rebuilt (rebuild-bundles.py); LATEST_VER in module-loader.js and all
three ?v= tags in main.html (core-bundle, module-loader, critical-ext-bundle)
bumped v4.6.101 -> v4.6.102.

Verification:
  $ node --check modules/core/module-system.js
  SYNTAX OK
  $ node --check modules/core/core-bundle.js
  BUNDLE SYNTAX OK
  $ node modules/test/test-vfs-checkpoint.js   (x5)
  test-vfs-checkpoint: 10 passed, 0 failed
  $ curl -s https://webx11.duckdns.org/spaces/newos4/main.html | grep -o 'core-bundle.js?v=[^"]*'
  core-bundle.js?v=v4.6.102
  $ python3 scripts/newos4-maintain.py
  PASS: version v4.6.102 x3 in main.html (expect 3) ... maintenance result: OK
  $ python3 scripts/newos4-skill-audit.py
  skill audit: 7/7 pass

1 files changed, 2 insertions, 3 deletions

diff --git a/modules/core/module-system.js b/modules/core/module-system.js
index b9b62a6..40b0861 100644
--- a/modules/core/module-system.js
+++ b/modules/core/module-system.js
@@ -479,9 +479,8 @@
                 this.commands['checkpoint'] = (args) => {
                     try {
                         const name = args[0] || '';
-                        this.terminal.fs.checkpoint(name);
-                        const displayName = name || new Date().toISOString();
-                        this.terminal.print('✅ Checkpoint created: ' + displayName, 'success');
+                        const created = this.terminal.fs.checkpoint(name);
+                        this.terminal.print('✅ Checkpoint created: ' + (created || name), 'success');
                     } catch (e) {
                         this.terminal.print('Checkpoint failed: ' + e.message, 'error');
                     }