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-dioxus/src/components/project_grid.rs

@@ -0,0 +1,32 @@
+/// ProjectGrid — responsive grid of ProjectBox cards.
+///
+/// Mirrors the Svelte app's ProjectGrid.svelte: CSS grid with
+/// auto-fit columns, minimum 28rem each.
+
+use dioxus::prelude::*;
+
+use crate::state::{AgentStatus, ProjectConfig};
+use crate::components::project_box::ProjectBox;
+
+#[component]
+pub fn ProjectGrid(projects: Vec<ProjectConfig>) -> Element {
+    // Assign different demo statuses to show variety
+    let statuses = vec![
+        AgentStatus::Running,
+        AgentStatus::Idle,
+        AgentStatus::Done,
+        AgentStatus::Stalled,
+    ];
+
+    rsx! {
+        div { class: "project-grid",
+            for (i, project) in projects.iter().enumerate() {
+                ProjectBox {
+                    key: "{project.id}",
+                    project: project.clone(),
+                    initial_status: statuses[i % statuses.len()],
+                }
+            }
+        }
+    }
+}