Document AltStore-only iPhone deployment

TESTING.md

@@ -121,8 +121,8 @@ xcrun simctl install booted "$gotcha_build_dir/Gotcha.app"
 xcrun simctl launch booted de.rfc1437.gotcha
 ```
 
-Before App Store submission, create a signed Release archive and inspect the
-packaged application rather than relying on Debug build settings:
+Before AltStore PAL release publication, create a signed Release archive and
+inspect the packaged application rather than relying on Debug build settings:
 
 ```sh
 cd ios
@@ -138,7 +138,13 @@ xcodebuild \
 Verify the archived app reports version `1.0` and a positive build number, is
 signed for distribution with the expected bundle identifier and entitlements,
 contains `PrivacyInfo.xcprivacy`, and declares the correct export-compliance
-answer before uploading it to App Store Connect.
+answer before uploading it to App Store Connect for notarization.
+
+Use the simulator for all development validation. Never install an Xcode-run or
+otherwise development-signed build on a physical iPhone because that would
+replace the correctly signed AltStore PAL installation. Physical-device release
+testing begins only after the accepted Alternative Distribution Package and
+source update are published, and installs or updates Gotcha through AltStore PAL.
 
 ## Add Server and native text editing
 
@@ -489,6 +495,7 @@ answer before uploading it to App Store Connect.
 - [ ] All build gates passed.
 - [ ] A signed Release archive passed the version, identity, entitlement,
       privacy-manifest, and export-compliance checks above.
-- [ ] Fresh-install and upgrade passes completed.
+- [ ] Fresh-install and upgrade passes completed through AltStore PAL on an
+      eligible physical iPhone.
 - [ ] Every supported iOS version and required device class completed.
 - [ ] Every scenario passed; any discovered failures were resolved and retested.