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/components/project_grid.rs

@@ -0,0 +1,80 @@
+//! ProjectGrid: flex-wrap grid of ProjectBox cards.
+//!
+//! Lays out projects in a responsive grid that wraps when the window is wide
+//! enough for multiple columns.
+
+use gpui::*;
+
+use crate::components::project_box::ProjectBox;
+use crate::state::AppState;
+use crate::theme;
+
+// ── ProjectGrid View ────────────────────────────────────────────────
+
+pub struct ProjectGrid {
+    app_state: Entity<AppState>,
+    /// One ProjectBox entity per project.
+    project_boxes: Vec<Entity<ProjectBox>>,
+}
+
+impl ProjectGrid {
+    pub fn new(app_state: Entity<AppState>, cx: &mut Context<Self>) -> Self {
+        // Clone projects out of state to avoid borrowing cx through app_state
+        let projects: Vec<_> = {
+            let state = app_state.read(cx);
+            state.projects.clone()
+        };
+
+        let project_boxes: Vec<Entity<ProjectBox>> = projects
+            .into_iter()
+            .map(|proj| {
+                cx.new(|cx| {
+                    let mut pb = ProjectBox::new(proj);
+                    pb.init_subviews(cx);
+                    pb
+                })
+            })
+            .collect();
+
+        Self {
+            app_state,
+            project_boxes,
+        }
+    }
+}
+
+impl Render for ProjectGrid {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        let mut grid = div()
+            .id("project-grid")
+            .flex_1()
+            .w_full()
+            .h_full()
+            .flex()
+            .flex_row()
+            .flex_wrap()
+            .gap(px(8.0))
+            .p(px(8.0))
+            .bg(theme::CRUST)
+            .overflow_y_scroll();
+
+        for pb in &self.project_boxes {
+            grid = grid.child(pb.clone());
+        }
+
+        if self.project_boxes.is_empty() {
+            grid = grid.child(
+                div()
+                    .flex_1()
+                    .flex()
+                    .items_center()
+                    .justify_center()
+                    .text_size(px(16.0))
+                    .text_color(theme::OVERLAY0)
+                    .child("No projects. Press Ctrl+N to add one."),
+            );
+        }
+
+        grid
+    }
+}