Add nested thread trees, recursive reply fetching, multi-level back navigation

Overhauls the thread view from flat single-level replies to proper nested
conversation trees. Fixes NIP-10 tagging (root + reply markers), adds
2-round-trip recursive thread fetch, ancestor chain display, reply-to-any-note
targeting, view stack navigation (up to 20 levels), and loading shimmer.

src/stores/ui.test.ts

@@ -9,6 +9,7 @@ describe("useUIStore", () => {
       selectedPubkey: null,
       selectedNote: null,
       previousView: "feed",
+      viewStack: [],
       feedTab: "global",
       pendingSearch: null,
       pendingDMPubkey: null,

src/stores/ui.ts

@@ -5,12 +5,21 @@ import { NDKEvent } from "@nostr-dev-kit/ndk";
 type View = "feed" | "search" | "relays" | "settings" | "profile" | "thread" | "article-editor" | "article" | "articles" | "media" | "podcasts" | "about" | "zaps" | "dm" | "notifications" | "bookmarks" | "hashtag";
 type FeedTab = "global" | "following" | "trending";
 
+interface ViewStackEntry {
+  view: View;
+  selectedNote: NDKEvent | null;
+  selectedPubkey: string | null;
+}
+
+const MAX_STACK = 20;
+
 interface UIState {
   currentView: View;
   sidebarCollapsed: boolean;
   selectedPubkey: string | null;
   selectedNote: NDKEvent | null;
   previousView: View;
+  viewStack: ViewStackEntry[];
   feedTab: FeedTab;
   pendingSearch: string | null;
   pendingDMPubkey: string | null;
@@ -22,7 +31,7 @@ interface UIState {
   setView: (view: View) => void;
   setFeedTab: (tab: FeedTab) => void;
   openProfile: (pubkey: string) => void;
-  openThread: (note: NDKEvent, from: View) => void;
+  openThread: (note: NDKEvent, from?: View) => void;
   openSearch: (query: string) => void;
   openHashtag: (tag: string) => void;
   openDM: (pubkey: string) => void;
@@ -41,6 +50,7 @@ export const useUIStore = create<UIState>((set, _get) => ({
   selectedPubkey: null,
   selectedNote: null,
   previousView: "feed",
+  viewStack: [],
   feedTab: "global",
   pendingSearch: null,
   pendingDMPubkey: null,
@@ -51,17 +61,32 @@ export const useUIStore = create<UIState>((set, _get) => ({
   feedLanguageFilter: null,
   setView: (currentView) => set({ currentView }),
   setFeedTab: (feedTab) => set({ feedTab }),
-  openProfile: (pubkey) => set((s) => ({ currentView: "profile", selectedPubkey: pubkey, previousView: s.currentView as View })),
-  openThread: (note, from) => set({ currentView: "thread", selectedNote: note, previousView: from }),
+  openProfile: (pubkey) => set((s) => {
+    const stack = [...s.viewStack, { view: s.currentView, selectedNote: s.selectedNote, selectedPubkey: s.selectedPubkey }].slice(-MAX_STACK);
+    return { currentView: "profile", selectedPubkey: pubkey, previousView: s.currentView as View, viewStack: stack };
+  }),
+  openThread: (note, _from) => set((s) => {
+    const stack = [...s.viewStack, { view: s.currentView, selectedNote: s.selectedNote, selectedPubkey: s.selectedPubkey }].slice(-MAX_STACK);
+    return { currentView: "thread", selectedNote: note, previousView: s.currentView as View, viewStack: stack };
+  }),
   openSearch: (query) => set({ currentView: "search", pendingSearch: query }),
-  openHashtag: (tag) => set((s) => ({ currentView: "hashtag", pendingHashtag: tag, previousView: s.currentView as View })),
+  openHashtag: (tag) => set((s) => {
+    const stack = [...s.viewStack, { view: s.currentView, selectedNote: s.selectedNote, selectedPubkey: s.selectedPubkey }].slice(-MAX_STACK);
+    return { currentView: "hashtag", pendingHashtag: tag, previousView: s.currentView as View, viewStack: stack };
+  }),
   openDM: (pubkey) => set({ currentView: "dm", pendingDMPubkey: pubkey }),
-  openArticle: (naddr, event) => set((s) => ({ currentView: "article", pendingArticleNaddr: naddr, pendingArticleEvent: event ?? null, previousView: s.currentView as View })),
-  goBack: () => set((s) => ({
-    showHelp: false,
-    currentView: s.previousView !== s.currentView ? s.previousView : "feed",
-    selectedNote: null,
-  })),
+  openArticle: (naddr, event) => set((s) => {
+    const stack = [...s.viewStack, { view: s.currentView, selectedNote: s.selectedNote, selectedPubkey: s.selectedPubkey }].slice(-MAX_STACK);
+    return { currentView: "article", pendingArticleNaddr: naddr, pendingArticleEvent: event ?? null, previousView: s.currentView as View, viewStack: stack };
+  }),
+  goBack: () => set((s) => {
+    const stack = [...s.viewStack];
+    const prev = stack.pop();
+    if (prev) {
+      return { showHelp: false, currentView: prev.view, selectedNote: prev.selectedNote, selectedPubkey: prev.selectedPubkey, viewStack: stack };
+    }
+    return { showHelp: false, currentView: "feed", selectedNote: null, viewStack: [] };
+  }),
   setFeedLanguageFilter: (feedLanguageFilter) => set({ feedLanguageFilter }),
   toggleSidebar: () => set((s) => {
     const next = !s.sidebarCollapsed;