docs(ios): document custom bundle-ID suffix for a separate build

Explains appending a unique suffix (e.g. .pixel) to the app + extension
bundle IDs (and matching tunnelId) to install a parallel build without
claiming the reserved com.therealaleph.mhrv ID. Local-only; not committed.

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

Author: yyoyoian-pixel

ios/README.md

@@ -61,6 +61,29 @@ The app version comes from `MARKETING_VERSION` / `CURRENT_PROJECT_VERSION` in
 Keep `MARKETING_VERSION` in sync with the crate version in `Cargo.toml`. After
 changing it, run `xcodegen generate`.
 
+## Building a separate copy (own bundle ID)
+
+The committed bundle ID `com.therealaleph.mhrv` is reserved for the main release.
+A bundle ID is globally unique across all of Apple, so if you want to ship your
+own build (e.g. a personal TestFlight build that installs **alongside** the main
+app without claiming its ID), append a unique suffix to the IDs **locally** —
+do **not** commit this. Use `.pixel` (or your own):
+
+1. `ios/project.yml` — app target:
+   `PRODUCT_BUNDLE_IDENTIFIER: com.therealaleph.mhrv` → `com.therealaleph.mhrv.pixel`
+2. `ios/project.yml` — `MhrvTunnel` target (the extension ID **must** stay a child
+   of the app ID):
+   `com.therealaleph.mhrv.tunnel` → `com.therealaleph.mhrv.pixel.tunnel`
+3. `ios/App/ContentView.swift` — `VpnManager.tunnelId` must equal the extension ID:
+   `"com.therealaleph.mhrv.tunnel"` → `"com.therealaleph.mhrv.pixel.tunnel"`
+4. (Optional, for a fully independent data container) change the App Group in both
+   `*.entitlements` and the `groupId` strings in `ContentView.swift` /
+   `PacketTunnelProvider.swift` to `group.com.therealaleph.mhrv.pixel`.
+5. `cd ios && xcodegen generate`, then create the App Store Connect record for the
+   new bundle ID.
+
+Keep these edits out of any PR to the main repo.
+
 ## Publishing to TestFlight
 
 1. **Bump the version.** Edit `MARKETING_VERSION` (and bump `CURRENT_PROJECT_VERSION`,