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/command_palette.rs

@@ -0,0 +1,85 @@
+/// CommandPalette — Ctrl+K overlay with search and command list.
+///
+/// Mirrors the Svelte app's CommandPalette.svelte: Spotlight-style overlay
+/// with search input and filtered command list.
+
+use dioxus::prelude::*;
+
+use crate::state::{palette_commands, PaletteCommand};
+
+#[component]
+pub fn CommandPalette(
+    visible: Signal<bool>,
+) -> Element {
+    let mut search = use_signal(|| String::new());
+    let commands = palette_commands();
+
+    // Filter commands by search text
+    let search_text = search.read().to_lowercase();
+    let filtered: Vec<&PaletteCommand> = if search_text.is_empty() {
+        commands.iter().collect()
+    } else {
+        commands
+            .iter()
+            .filter(|c| c.label.to_lowercase().contains(&search_text))
+            .collect()
+    };
+
+    let close = move |_| {
+        visible.set(false);
+        search.set(String::new());
+    };
+
+    let on_key = move |e: KeyboardEvent| {
+        if e.key() == Key::Escape {
+            visible.set(false);
+            search.set(String::new());
+        }
+    };
+
+    if !*visible.read() {
+        return rsx! {};
+    }
+
+    rsx! {
+        div {
+            class: "palette-overlay",
+            onclick: close,
+            onkeydown: on_key,
+
+            div {
+                class: "palette-box",
+                // Stop click propagation so clicking inside doesn't close
+                onclick: move |e| e.stop_propagation(),
+
+                input {
+                    class: "palette-input",
+                    r#type: "text",
+                    placeholder: "Type a command...",
+                    value: "{search}",
+                    oninput: move |e| search.set(e.value()),
+                    autofocus: true,
+                }
+
+                div { class: "palette-results",
+                    for cmd in filtered.iter() {
+                        div { class: "palette-item",
+                            span { class: "palette-item-icon", "{cmd.icon}" }
+                            span { class: "palette-item-label", "{cmd.label}" }
+                            if let Some(ref shortcut) = cmd.shortcut {
+                                span { class: "palette-item-shortcut", "{shortcut}" }
+                            }
+                        }
+                    }
+
+                    if filtered.is_empty() {
+                        div {
+                            style: "padding: 1rem; text-align: center; color: var(--ctp-overlay0); font-size: 0.8125rem;",
+                            "No matching commands"
+                        }
+                    }
+                }
+            }
+        }
+    }
+}