[bmc08gt]

Syncs the contract to flipcash2-protobuf-api@b655df17 (upstream #157, #158, #159) and adds the 0.22.0 changelog entry. Release as 0.22.0.

This upgrade breaks source in Swift only. GetKeyEnvelopeResponse.key_envelope moved into a new oneof envelope, so hasKeyEnvelope is gone. Field numbers are unchanged, so the wire format is not affected.

Contract changes

• Group invites: CreateInvite, GetInvite, GetChatInvites, RevokeInvite on chat.v1.Chat, with Invite, InviteId, InviteToken, InviteKeyEnvelope and InviteSecretEnvelope. JoinChatRequest.invite (field 2) joins a private group with an invite. ViewerState.Permissions.can_invite (field 3).
• Key envelopes: GetKeyEnvelopeResponse.invite_key_bundle (oneof field 5) for a member who joined with an invite and hasn't stored their own envelope yet, plus wrapped_by_public_key (field 4).
• Anonymous reads: GetInvite and GetRoster (new invite_token, field 3) accept an invite token without auth. GetChat on a private group without auth returns its Metadata record instead of DENIED.
• messaging.v1.SystemContent: member-joined oneof gains invited (field 4).
• common.v1.Username: 2 to 30 characters, up from 15.
• Appended enum cases: JoinChatResponse.Result INVITE_NOT_FOUND = 5 through INVITE_REVOKED = 8. Nothing was renumbered.

App PRs

Both are drafts. They contain only the scaffolding and stay blocked until 0.22.0 is published and their pins move. Neither implements the invite crypto or UI, and neither raises the 15-character username limit.

• Android: feat(chat): scaffold flipcash2 0.22.0 group invites code-android-app#1863
• iOS: feat(chat): scaffold flipcash2 0.22.0 group invites code-ios-app#1141