docs: verify Ubuntu 22.04 + air-gapped deployment (Rev 3.1)

Tested in two separate Ubuntu 22.04 Docker containers:
- Container 1 (online): Clone, setup, fetch 510/510 ✅
- Container 2 (air-gapped): BB_NO_NETWORK=1 fetch 510/510 ✅

Updated verification table with two new rows:
- Ubuntu 22.04 host: ✅
- Air-gapped fetch (BB_NO_NETWORK=1): ✅

docs/02-mirror-creation/step-by-step-mirror-creation.md

@@ -2,7 +2,7 @@
 
 **Document ID:** PROC-MIRROR-001-REV3
 **Date:** 2026-03-01
-**Verified:** 2026-03-01 (all steps tested on Debian 13 / sandbox)
+**Verified:** 2026-03-01 (Debian 13 + Ubuntu 22.04 Docker, incl. air-gapped deployment)
 **System:** Ubuntu 22.04 LTS (recommended), Debian 12/13 (works with warning)
 **Target:** TQMa6UL Yocto Scarthgap mirror (UT build)
 
@@ -274,9 +274,11 @@ bitbake tq-image-small-debug
 | License extraction | ✅ | 264/264 recipes, 224 URLs |
 | ci/ls-machines | ✅ | tqma6ul-multi-mba6ulx found |
 | Debian 13 host | ✅ | Warning but functional |
-| Full build | ⬜ | Not tested (sandbox RAM limit) |
+| Ubuntu 22.04 host | ✅ | Tested in Docker, all steps pass |
+| Air-gapped fetch (BB_NO_NETWORK=1) | ✅ | 510/510 from local mirror |
+| Full build | ⬜ | Not tested (sandbox RAM limit, needs 8GB+) |
 
 ---
 
 **Author:** Siggi ⚙️
-**Revision:** 3.0 (verified)
+**Revision:** 3.1 (Ubuntu 22.04 + air-gap verified)