feat: add Dioxus and GPUI UI prototypes for framework comparison

Dioxus (ui-dioxus/): 2,169 lines, WebView mode (same wry as Tauri),
  Catppuccin theme, 12 components, agor-core integration, compiles clean.
  Evolution path — keeps xterm.js, gradual migration from Tauri.

GPUI (ui-gpui/): 2,490 lines, GPU-accelerated rendering, alacritty_terminal
  for native terminal, 17 files, Catppuccin palette, demo data.
  Revolution path — pure Rust UI, 120fps target, no WebView.

Both are standalone (not in workspace), share agor-core backend.
Created for side-by-side comparison to inform framework decision.

ui-gpui/src/workspace.rs

@@ -0,0 +1,120 @@
+//! Main workspace layout: sidebar + settings drawer + project grid + status bar.
+//!
+//! This is the root view that composes all sub-components into the IDE-like layout.
+
+use gpui::*;
+
+use crate::components::command_palette::CommandPalette;
+use crate::components::project_grid::ProjectGrid;
+use crate::components::settings::SettingsPanel;
+use crate::components::sidebar::Sidebar;
+use crate::components::status_bar::StatusBar;
+use crate::state::AppState;
+use crate::theme;
+
+// ── Workspace View ──────────────────────────────────────────────────
+
+pub struct Workspace {
+    app_state: Entity<AppState>,
+    sidebar: Entity<Sidebar>,
+    settings_panel: Entity<SettingsPanel>,
+    project_grid: Entity<ProjectGrid>,
+    status_bar: Entity<StatusBar>,
+    command_palette: Entity<CommandPalette>,
+}
+
+impl Workspace {
+    pub fn new(app_state: Entity<AppState>, cx: &mut Context<Self>) -> Self {
+        let sidebar = cx.new({
+            let state = app_state.clone();
+            |_cx| Sidebar::new(state)
+        });
+        let settings_panel = cx.new({
+            let state = app_state.clone();
+            |_cx| SettingsPanel::new(state)
+        });
+        let project_grid = cx.new({
+            let state = app_state.clone();
+            |cx| ProjectGrid::new(state, cx)
+        });
+        let status_bar = cx.new({
+            let state = app_state.clone();
+            |_cx| StatusBar::new(state)
+        });
+        let command_palette = cx.new({
+            let state = app_state.clone();
+            |_cx| CommandPalette::new(state)
+        });
+
+        // Observe app_state changes to trigger re-renders
+        cx.observe(&app_state, |_this, _entity, cx| {
+            cx.notify();
+        })
+        .detach();
+
+        Self {
+            app_state,
+            sidebar,
+            settings_panel,
+            project_grid,
+            status_bar,
+            command_palette,
+        }
+    }
+}
+
+impl Render for Workspace {
+    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let state = self.app_state.read(cx);
+        let sidebar_open = state.sidebar_open;
+        let settings_open = state.settings_open;
+        let palette_open = state.palette_open;
+
+        let mut root = div()
+            .id("workspace-root")
+            .size_full()
+            .flex()
+            .flex_col()
+            .bg(theme::CRUST)
+            .font_family("Inter");
+
+        // ── Main content row (sidebar + settings? + grid) ───
+        let mut main_row = div()
+            .id("main-row")
+            .flex_1()
+            .w_full()
+            .flex()
+            .flex_row()
+            .overflow_hidden();
+
+        // Sidebar (icon rail)
+        if sidebar_open {
+            main_row = main_row.child(self.sidebar.clone());
+        }
+
+        // Settings drawer (between sidebar and grid)
+        if settings_open {
+            main_row = main_row.child(self.settings_panel.clone());
+        }
+
+        // Project grid (fills remaining space)
+        main_row = main_row.child(
+            div()
+                .flex_1()
+                .h_full()
+                .child(self.project_grid.clone()),
+        );
+
+        root = root.child(main_row);
+
+        // ── Status bar (bottom) ─────────────────────────────
+        root = root.child(self.status_bar.clone());
+
+        // ── Command palette overlay (if open) ───────────────
+        if palette_open {
+            root = root.child(self.command_palette.clone());
+        }
+
+        root
+    }
+}