Add UI button registration API (registerButton, unregisterButton, getButtonsForLocation)

dist/PluginInterfaces.d.ts

@@ -139,6 +139,8 @@ export interface PluginContext {
     ui: {
         registerRenderer: (type: string, renderer: CustomRenderer) => void;
         unregisterRenderer: (type: string) => void;
+        registerButton: (button: UIButtonDefinition) => void;
+        unregisterButton: (buttonId: string) => void;
     };
     /** Settings API */
     settings: {
@@ -188,7 +190,47 @@ export interface PluginSettingsSection {
     component: unknown;
 }
 /** UI locations where plugins can inject content. */
-export type UILocation = 'room-header' | 'message-actions' | 'user-menu' | 'room-menu' | 'composer-actions';
+export type UILocation = 'room-header' | 'message-actions' | 'user-menu' | 'room-menu' | 'composer-actions' | 'channel-list' | 'direct-messages' | 'home-section' | 'search-notification-section' | 'text-composer-toolbar' | 'sidebar-actions';
+/**
+ * Button positioning configuration for plugins.
+ * Allows buttons to be placed before or after existing elements or groups.
+ */
+export interface UIButtonPosition {
+    /** Place button before this element/group ID */
+    before?: string;
+    /** Place button after this element/group ID */
+    after?: string;
+    /**
+     * Optional group ID this button belongs to.
+     * Buttons in the same group are rendered together.
+     */
+    group?: string;
+    /** Order within the group (lower numbers appear first) */
+    order?: number;
+}
+/**
+ * Definition for a UI button registered by a plugin.
+ * Framework-agnostic - the component/element is passed as unknown.
+ */
+export interface UIButtonDefinition {
+    /** Unique ID for this button */
+    id: string;
+    /** Location where the button should appear */
+    location: UILocation;
+    /** Button label or tooltip */
+    label: string;
+    /** Optional icon identifier */
+    icon?: string;
+    /** Positioning configuration */
+    position?: UIButtonPosition;
+    /**
+     * The actual button component or render function.
+     * Framework-agnostic - hosts using React should cast to ReactNode.
+     */
+    component: unknown;
+    /** Optional callback when clicked (if component doesn't handle it) */
+    onClick?: () => void | Promise<void>;
+}
 /**
  * The main plugin interface that all plugins must implement.
  */