docs(naming): adopt OS / Enhanced product-line framing + align with existing repos

Two product lines, named to make scope obvious to buyers:
- 🔒 SilverMetal OS — we ship the operating system or ROM
  (Linux, Pixel, Samsung-unlocked, Motorola-unlocked)
- 🛡️ SilverMetal Enhanced — we harden the OS the device already runs
  (Windows, macOS, iOS, generic Android)

Repo alignment:
- SilverVPN already exists as a SilverLABS product (server + MAUI client +
  Linux client + tunnel service). stack/vpn/ is now an integration pointer
  rather than a re-scaffold; per-platform READMEs reference it.
- SilverApple is deprecated; SilverMetal Enhanced — iOS supersedes it.
  Migration step added as roadmap milestone 3I.1.
- SilverDROID name clash explicitly noted as unrelated (it's the SilverSHELL
  AppStore Android client, not an Android ROM).
- SilverChat may overlap with SilverVPN.Client.Chat; alignment decision
  added as roadmap milestone 1.1.1.

Roadmap restructured: phases now track the OS/Enhanced split.
Platform matrix re-sectioned and decision flowchart updated.
README rewritten around the two-product-line framing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

windows/README.md

@@ -1,6 +1,8 @@
-# SilverMetal Windows
+# SilverMetal Enhanced — Windows
 
-**Status**: Phase 3 (planning, post-Linux v1)
+**Status**: Phase 3W (planning, post-Linux v1)
+
+🛡️ **SilverMetal Enhanced product line** — we harden Windows in place; we do not ship a custom Windows kernel (Microsoft does not permit that).
 
 Tier C — config-layer hardening only. Honest positioning: we cannot modify the Windows kernel or boot chain; we turn every dial Microsoft exposes.
 
@@ -16,6 +18,7 @@ LTSC IoT-based installer that transforms a vanilla Windows install into a Silver
 - Telemetry blocked at hosts file + service + GP layers
 - Edge / Chrome replaced with SilverBrowser default
 - Full SilverLABS Stack preinstalled (native Windows builds)
+- SilverVPN MAUI Windows client integrated from existing [`SilverLABS/SilverVPN`](https://git.silverlabs.uk/SilverLABS/SilverVPN)
 
 ## Out of scope
 
@@ -25,7 +28,7 @@ LTSC IoT-based installer that transforms a vanilla Windows install into a Silver
 
 ## Directory layout
 
-To be populated in Phase 3. Initial structure planned:
+To be populated in Phase 3W. Initial structure planned:
 
 ```
 windows/
@@ -49,3 +52,4 @@ windows/
 - **Windows 11 IoT Enterprise LTSC** — base OS (licensed)
 - **AtlasOS / ReviOS / privacy.sexy** — reference for hardening configs
 - **Chris Titus Tech / O&O ShutUp10** — reference for telemetry blocking
+- **`SilverLABS/SilverVPN`** — MAUI Windows client (existing)