feat(app)!: no anonymous accounts on the device (ADR 0020, D4, D25)

Every account has a way in, so the apps make no anonymous account any
more. The start screen shows whenever nobody is signed in, a first
start included, and offers SimpleLogin, a password and GitHub for those
who have it, with no start without an account. An instance out of reach
is said so, with Try again, and one offering no way to create an account
too. An anonymous account's session left from before is deleted as the
app starts (D25), falling back to signing out on the device.

What only anonymous accounts needed goes: signing in anonymously, the
signed-out mark, adding GitHub to an account and switching to a GitHub
account from the Profile tab (with its Cancel, the only one), an
anonymous device's own keys, the warning that signing out deletes the
account, and the texts about keeping progress. Settings says on which
instance the account is signed in. Learn's publishing, reports and
suggestions and its learner count no longer ask whether the person has
an identity: everyone signed in has one.

The server still offers anonymous sign-in until the next commit, so
older apps keep working until v0.20.0 raises the minimum build.

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/lib/l10n/halkyon_app_en.arb

@@ -116,10 +116,9 @@
   "accountAdd": "Add account",
   "accountAddSubtitle": "Choose the instance for the account to add.",
   "accountSignedIn": "Signed in",
-  "accountAnonymous": "Anonymous",
   "accountRemoveTooltip": "Remove account",
   "accountRemoveTitle": "Remove account?",
-  "accountRemoveMessage": "Removes the account on {name} from this device, with all the device holds of it. What it synced stays on {name}: sign in there again to have it. An anonymous account can't be signed into again.",
+  "accountRemoveMessage": "Removes the account on {name} from this device, with all the device holds of it. What it synced stays on {name}: sign in there again to have it.",
   "@accountRemoveMessage": {
     "placeholders": {
       "name": {
@@ -136,17 +135,8 @@
       }
     }
   },
-  "accountAnonymousOn": "Anonymous on {instance}",
-  "@accountAnonymousOn": {
-    "placeholders": {
-      "instance": {
-        "type": "String"
-      }
-    }
-  },
   "accountSwitch": "Switch account",
   "accountSignOut": "Sign out",
-  "accountSignOutTitle": "Sign out?",
   "accountDelete": "Delete account",
   "accountDeleteTitle": "Delete your account?",
   "accountSignOutFailed": "Couldn't sign out on this device. Try again.",
@@ -165,22 +155,28 @@
     }
   },
   "startWithGitHub": "Sign in with GitHub",
-  "startWithoutAccount": "Start without an account",
-  "startAnonymous": "Progress is saved on this device. Sign in to keep it.",
   "startGitHubFailed": "Couldn't sign in with GitHub.",
-  "startNoGitHubAccount": "No account here signs in with this GitHub account yet.",
+  "startNoGitHubAccount": "No account here signs in with this GitHub account.",
   "gitHubCreateAccountInstead": "Create an account with your email address and a password instead.",
   "@gitHubCreateAccountInstead": {
     "description": "Said after a GitHub account nobody on the instance signs in with, where people sign in with a password and GitHub is added to nobody (ADR 0017)."
   },
-  "gitHubNoAccountSetUpPassword": "No account here signs in with this GitHub account yet. To keep your progress, set up a password instead.",
-  "@gitHubNoAccountSetUpPassword": {
-    "description": "An anonymous person signed in with a GitHub account nobody here has, where GitHub is added to nobody: the password set up below keeps their account."
+  "gitHubSimpleLoginInstead": "Continue with SimpleLogin to create one instead.",
+  "@gitHubSimpleLoginInstead": {
+    "description": "Said after a GitHub account nobody on the instance signs in with, where the instance offers SimpleLogin (ADR 0020): GitHub makes no account."
   },
   "gitHubUsePassword": "This account signs in with its email address and password now, not with GitHub.",
-  "gitHubDeprecated": "GitHub can't be added as a way to sign in any more: your email address and password are.",
   "gitHubEnded": "Sign-in with GitHub has ended on this instance.",
   "startOtherInstance": "Use another instance",
+  "startNoWay": "{instance} offers no way to create an account.",
+  "@startNoWay": {
+    "description": "On the start screen, where the instance offers neither SimpleLogin nor a password (ADR 0020, D4): nobody can make an account there.",
+    "placeholders": {
+      "instance": {
+        "type": "String"
+      }
+    }
+  },
   "syncTitle": "Sync",
   "syncNow": "Sync now",
   "syncStateSyncing": "Syncing…",