Add Hello Plugin with settings pane and metadata

plugins/ohn-plugin-hello/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "ohn-plugin-hello"
+version = "0.1.0"
+edition = "2024"
+
+[package.metadata.hotplug.api_versions]
+OhnUiPlugin = "1.0"
+
+[dependencies]
+ohn-ui-plugin  = { workspace = true }
+hotplug-meta   = { workspace = true }
+inventory      = { workspace = true }
+gpui           = { workspace = true }

plugins/ohn-plugin-hello/src/lib.rs

@@ -0,0 +1,74 @@
+use gpui::prelude::*;
+use gpui::*;
+use ohn_ui_plugin::{OhnUiPlugin, PluginSettingsPane, PluginSidePanel};
+
+/// Hello Plugin — a minimal demo of contributing a settings pane via OhnUiPlugin.
+#[derive(Default)]
+pub struct HelloPlugin;
+
+impl hotplug_meta::PluginMeta for HelloPlugin {
+    fn id() -> &'static str {
+        "org.devism.hello-plugin"
+    }
+    fn name() -> &'static str {
+        "Hello Plugin"
+    }
+    fn version() -> &'static str {
+        env!("CARGO_PKG_VERSION")
+    }
+}
+
+impl OhnUiPlugin for HelloPlugin {
+    fn settings_pane(&self) -> Option<PluginSettingsPane> {
+        Some(PluginSettingsPane {
+            label: "Hello",
+            icon_name: "star",
+            build: std::sync::Arc::new(|_window, cx| cx.new(|_cx| HelloView).into()),
+        })
+    }
+
+    fn side_panel(&self) -> Option<PluginSidePanel> {
+        None
+    }
+}
+
+ohn_ui_plugin::register_ohn_ui_plugin!(HelloPlugin);
+
+// ---------------------------------------------------------------------------
+// Settings pane view
+// ---------------------------------------------------------------------------
+
+struct HelloView;
+
+impl Render for HelloView {
+    fn render(
+        &mut self,
+        _window: &mut Window,
+        _cx: &mut Context<Self>,
+    ) -> impl IntoElement {
+        div()
+            .flex()
+            .flex_col()
+            .items_center()
+            .justify_center()
+            .gap(px(16.0))
+            .p(px(40.0))
+            .child(
+                div()
+                    .text_size(px(28.0))
+                    .child("👋"),
+            )
+            .child(
+                div()
+                    .text_size(px(18.0))
+                    .font_weight(FontWeight::SEMIBOLD)
+                    .child("Hello from the Hello Plugin!"),
+            )
+            .child(
+                div()
+                    .text_size(px(13.0))
+                    .text_color(gpui::rgb(0x888888))
+                    .child("This demo plugin was installed via the hotplug registry."),
+            )
+    }
+}