fix(reader): pass a real per-document id to NativeTextViewWrapper

Every document was using the library's literal "default" documentId
— never our own viewModel.documentId — meaning undo stacks, content-
divergence snapshots, scroll-offset memory, and pending inline
replacements were all keyed to the same slot across every document
instead of being scoped per-document. That's a real, unambiguous bug
regardless of the click/cursor issue: opening a second document could
replay or discard the wrong document's undo history.

Investigated the click-does-nothing-in-edit-mode report by reading
through the library's (vendored, external — swift-markdown-engine)
own isEditable/isSelectable wiring in both makeNSView and updateNSView
directly; both looked correctly applied on every pass, and a clean-
relaunch test ruled out the settings/NavigationSplitView bug from
earlier in this session as the cause. Couldn't confirm this documentId
fix resolves the click issue without being able to run the app here —
worth retesting either way.

Outpost/Features/Collections/DocumentReaderView.swift

@@ -92,6 +92,7 @@ struct DocumentReaderView: View {
                     NativeTextViewWrapper(
                         text: $viewModel.text,
                         configuration: .init(heightBehavior: .fitsContent),
+                        documentId: viewModel.documentId,
                         isEditable: viewModel.isEditing
                     )