Demo app fails to build on newer Xcode: ExyteChat 2.x needs a 3.x migration

[nezhyborets]

What

The Demo app (Demo/Demo.xcodeproj) currently fails to link on Xcode 27.0:

Undefined symbols for architecture arm64/x86_64:
  "variable initialization expression of ExyteChat.ChatView.(__isShowingMenu...) : SwiftUI.LazyState<Swift.Bool>", referenced from: ...

Demo/DemoChat is pinned to .package(url: "https://github.com/exyte/Chat.git", from: "2.5.7"), which currently resolves to 2.7.10 (the latest 2.x release). That version's ChatView default-property-initializer symbol doesn't link against this newer Swift compiler/SDK.

Why it's not a quick fix

Bumping the dependency to the latest release (3.3.0) does fix the linker error, but ExyteChat 2.x → 3.x is a breaking API change, and DemoChat's own source was written against the 2.x API. Confirmed compile errors after bumping to 3.3.0:

• ChatView no longer has a .messageUseMarkdown modifier (used in DetailView.swift and ResponsesChatDetailView.swift)
• PopupParameters lost its .displayMode member (surfaces via ExyteMediaPicker, which also gets bumped forward as a transitive dependency of Chat 3.x)
• ResponsesStore.ConversationTurn no longer conforms to Hashable (likely a conformance dropped by a Chat/MediaPicker 3.x type it wraps)

So this needs a deliberate ExyteChat 3.x migration of DemoChat, not a version bump alone.

Impact

• Demo is not built by any CI workflow, so this doesn't block CI or the package itself — only local development/testing of the Demo app.
• Anyone trying to run the Demo app locally on a recent Xcode toolchain will hit this.

Suggested next step

Migrate DemoChat to ExyteChat 3.3.0+: update Demo/DemoChat/Package.swift's version constraint, then fix the resulting compile errors (messageUseMarkdown, PopupParameters.displayMode, ConversationTurn: Hashable) per ExyteChat's 3.x migration notes.

Related: #443