fix(concord): clarify invite failure copy for token/decrypt mismatch

concord_invite_failed_incompatible is shown for the Unreadable status,
which fires both for a genuinely newer bundle format AND for the far more
common case where the fragment's unlock token does not decrypt the
published kind-33301 bundle (a stale link, or a coordinate re-posted under
a new token). The old copy asserted "created with a newer version of the
app", which is usually wrong, and suggested "try again after updating"
even though this state is non-retryable.

Reword to lead with the likely cause (outdated/replaced link), keep the
newer-version case as a secondary possibility, and point the user at
getting a fresh invite link.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0157AWJNEzybTuegstbWiQ6B

amethyst/src/main/res/values/strings.xml

@@ -310,7 +310,7 @@
     <string name="concord_redeeming_invite">Redeeming invite…</string>
     <string name="concord_invite_failed">Could not fetch this invite. The link may be expired or its relays unreachable.</string>
     <string name="concord_invite_failed_invalid">This invite link is invalid or can\'t be opened with this account.</string>
-    <string name="concord_invite_failed_incompatible">This invite was created with a newer version of the app and can\'t be opened here yet. Ask for an updated link or try again after updating.</string>
+    <string name="concord_invite_failed_incompatible">This invite link can\'t be opened. It may be outdated or already replaced by a newer one, or created with a newer version of the app. Ask for a fresh invite link.</string>
     <string name="concord_invite_failed_revoked">This invite link has been revoked and can no longer be used. Ask for a new one.</string>
     <string name="concord_home_title">Concord Channels</string>
     <string name="concord_home_empty">You haven\'t joined any Concord Channels yet. Create one, or open an invite link.</string>