docs(windows): add ISO-builder design + scaffold the windows/ tree

Add windows/iso-builder.md: reproducible custom-packed-ISO pipeline design for
SilverMetal Enhanced - Windows on IoT Enterprise LTSC. Covers the licensing
frame (IoT = blessed channel for preinstalled custom images; self-apply stays a
builder), 7 build stages (verify/extract/DISM-service/inject-unattend/brand/
oscdimg-repack/attest), the offline-vs-first-boot-vs-firmware control split, an
honest reproducibility scope (pinned inputs + SBOM + attestation, NOT bit-
identical on Windows), and M0-M4 milestones.

Scaffold windows/ per the planned layout:
- installer/  build.ps1 (7-stage orchestrator, stages stubbed to M2),
              inputs.manifest.json (pinned-input schema), autounattend.xml
              (local-account OOBE), oem/SetupComplete.cmd (first-boot runner)
- hardening/  shared §A-H PowerShell modules + Verify-SilverMetalWindows.ps1
              (used by BOTH the ISO first-boot path and the self-apply track).
              BitLocker module enforces TPM+PIN and blocks TPM-only.
- policies/ wdac/ debloat/ stack-installer/ drivers/ tests/  scaffolded with
  READMEs; wdac/ documents audit->enforce; debloat/ flags Tiny11/NTLite as an
  anti-pattern; rename applocker/ -> wdac/ realised.

All 11 PowerShell scripts parse clean; manifest JSON + autounattend XML valid.
Module bodies are M1 scaffold (safe: log + policy-set; interactive/firmware
steps documented, not faked).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

windows/policies/README.md

@@ -0,0 +1,9 @@
+# windows/policies
+
+Group Policy / ADMX exports and the **offline-applicable baseline** (`.reg` / `.pol`)
+that `build.ps1` applies into the WIM via offline hive editing (telemetry floor,
+service disables). The online/runtime policy is applied by the `../hardening/`
+modules at first boot.
+
+Populated at **M2** by exporting the prototype unit's applied policy
+(`LGPO.exe` / registry export) after the `hardening/` modules run on the device.