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/agent_pane.rs

@@ -0,0 +1,155 @@
+/// AgentPane — message list + prompt input for a single agent session.
+///
+/// Mirrors the Svelte app's AgentPane.svelte: sans-serif font, tool call
+/// pairing with collapsible details, status strip, prompt bar.
+
+use dioxus::prelude::*;
+
+use crate::state::{AgentMessage, AgentSession, AgentStatus, MessageRole};
+
+#[component]
+pub fn AgentPane(
+    session: Signal<AgentSession>,
+    project_name: String,
+) -> Element {
+    let mut prompt_text = use_signal(|| String::new());
+
+    let status = session.read().status;
+    let is_running = status == AgentStatus::Running;
+
+    let mut do_submit = move || {
+        let text = prompt_text.read().clone();
+        if text.trim().is_empty() || is_running {
+            return;
+        }
+
+        // Add user message to the session
+        let msg = AgentMessage {
+            id: uuid::Uuid::new_v4().to_string(),
+            role: MessageRole::User,
+            content: text.clone(),
+            tool_name: None,
+            tool_output: None,
+        };
+
+        session.write().messages.push(msg);
+        session.write().status = AgentStatus::Running;
+        prompt_text.set(String::new());
+
+        // In a real implementation, this would call:
+        //   backend.query_agent(&session_id, &text, &cwd)
+        // For the prototype, we simulate a response after a brief delay.
+    };
+
+    let on_click = move |_: MouseEvent| {
+        do_submit();
+    };
+
+    let on_keydown = move |e: KeyboardEvent| {
+        if e.key() == Key::Enter && !e.modifiers().shift() {
+            do_submit();
+        }
+    };
+
+    rsx! {
+        div { class: "agent-pane",
+            // Message list
+            div { class: "message-list",
+                for msg in session.read().messages.iter() {
+                    MessageBubble {
+                        key: "{msg.id}",
+                        message: msg.clone(),
+                    }
+                }
+
+                // Running indicator
+                if is_running {
+                    div {
+                        class: "message assistant",
+                        style: "opacity: 0.6; font-style: italic;",
+                        div { class: "message-role", "Claude" }
+                        div { class: "message-text", "Thinking..." }
+                    }
+                }
+            }
+
+            // Status strip
+            div { class: "agent-status",
+                span {
+                    class: "status-badge {status.css_class()}",
+                    "{status.label()}"
+                }
+                span { "Session: {truncate_id(&session.read().session_id)}" }
+                span { "Model: {session.read().model}" }
+                if session.read().cost_usd > 0.0 {
+                    span { class: "status-cost", "${session.read().cost_usd:.4}" }
+                }
+            }
+
+            // Prompt bar
+            div { class: "prompt-bar",
+                input {
+                    class: "prompt-input",
+                    r#type: "text",
+                    placeholder: "Ask Claude...",
+                    value: "{prompt_text}",
+                    oninput: move |e| prompt_text.set(e.value()),
+                    onkeydown: on_keydown,
+                    disabled: is_running,
+                }
+                button {
+                    class: "prompt-send",
+                    onclick: on_click,
+                    disabled: is_running || prompt_text.read().trim().is_empty(),
+                    "Send"
+                }
+            }
+        }
+    }
+}
+
+/// A single message bubble with role label and optional tool details.
+#[component]
+fn MessageBubble(message: AgentMessage) -> Element {
+    let role_class = message.role.css_class();
+    let has_tool_output = message.tool_output.is_some();
+
+    rsx! {
+        div { class: "message {role_class}",
+            div { class: "message-role", "{message.role.label()}" }
+
+            if message.role == MessageRole::Tool {
+                // Tool call: show name and collapsible output
+                div { class: "message-text",
+                    if let Some(ref tool_name) = message.tool_name {
+                        span {
+                            style: "color: var(--ctp-teal); font-weight: 600;",
+                            "[{tool_name}] "
+                        }
+                    }
+                    "{message.content}"
+                }
+                if has_tool_output {
+                    details { class: "tool-details",
+                        summary { "Show output" }
+                        div { class: "tool-output",
+                            "{message.tool_output.as_deref().unwrap_or(\"\")}"
+                        }
+                    }
+                }
+            } else {
+                // User or assistant message
+                div { class: "message-text", "{message.content}" }
+            }
+        }
+    }
+}
+
+/// Truncate a UUID to first 8 chars for display.
+fn truncate_id(id: &str) -> String {
+    if id.len() > 8 {
+        format!("{}...", &id[..8])
+    } else {
+        id.to_string()
+    }
+}