fix(docs): final stale category references in build.md and CHANGELOG

- build.md: Category 9 -> Category 6 (environment checker)
- CHANGELOG.md: 12 validation categories -> 7 grounded validation categories

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013AZySkzowyq4Ne2hrSRRAL

Author: kristopherjturner

CHANGELOG.md

@@ -20,6 +20,6 @@ Do not edit this file manually.
 
 ### Initial scaffold (2026-06-10)
 
-- WinPE validation engine (`Start-AzlValidation.ps1`) with 12 validation categories
+- WinPE validation engine (`Start-AzlValidation.ps1`) with 7 grounded validation categories
 - Endpoint list (`endpoints.json`) with 121 Azure Local, Arc, and Dell OEM endpoints
 - `Build-WinPEImage.ps1` to assemble the bootable WinPE ISO

docs/getting-started/build.md

@@ -29,7 +29,7 @@ If your build machine has limited or no internet access, pre-download the PS7 LT
 ```
 
 !!! warning "Module not included in air-gapped builds"
-    Without `AzStackHci.EnvironmentChecker`, Category 9 (environment checker) is skipped.
+    Without `AzStackHci.EnvironmentChecker`, Category 6 (environment checker) is skipped.
     Pre-stage the module at `<WorkspacePath>\mount\Tools\Modules` before the unmount step, or
     run the module-based tests from a staging server post-OS.