docs(auth): what the third reading found, and Proton's rule (ADR 0017)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/README.md

@@ -69,7 +69,11 @@ Written as the apps are: Dart 3.13's primary constructors, Material from
   screens: the start screen's Sign in and Create an account,
   `showPasswordSignInSheet`, `showAccountSetupSheet`,
   `showAccountRecoverySheet`, and `AccountSecuritySection` for an app's
-  account part. Anonymous people get no keys until something is encrypted
+  account part. Every change of how the account is secured asks for the
+  password with the code, one answer per sheet (`OwnerAnswer`, the owner's
+  proof: a session alone gets no code checked); deleting by a code by mail
+  follows `secondFactorWorks`, as the instance tells it, and asks for the
+  address only where the device doesn't know it. Anonymous people get no keys until something is encrypted
   (step 4). Every build of an app needs a C compiler and make: sodium's build
   hook compiles libsodium.
 - **Files** (`FileSaver`, `PlatformFileSaver`): keeping a file the app made