feat: Add slashcommand api

docs-site/docs/plugin-development/api-reference.md

@@ -318,6 +318,55 @@ interface PluginApiDomMountRequest {
 | `ui.registerEmbedRenderer(id, contribution)`  | `ui.embeds`          | Adds an embed renderer.                                         |
 | `ui.mountElement(id, request)`                | `ui.dom`             | Mounts plugin-owned DOM into a target element or selector.      |
 
+## Slash Commands
+
+Slash commands appear in a Discord-style autocomplete menu when a user types `/` in the chat composer. A command with `scope: 'global'` (the default) is offered in every chat surface, including direct messages; a command with `scope: 'server'` only appears while a chat server is active. The user picks a command from the menu (or types it and presses Enter) and the `run` callback executes with the parsed arguments and the current interaction context.
+
+```ts
+type PluginApiSlashCommandScope = 'global' | 'server';
+
+interface PluginApiSlashCommandOption {
+  description?: string;
+  name: string;
+  required?: boolean;
+  // 'rest' captures all remaining text; otherwise a single whitespace-delimited token
+  type?: 'string' | 'number' | 'boolean' | 'rest';
+}
+
+interface PluginApiSlashCommandContext extends PluginApiActionContext {
+  args: Record<string, string>; // parsed values keyed by option name
+  command: string; // invoked name without the leading slash
+  rawArgs: string; // raw text typed after the command name
+}
+
+interface PluginApiSlashCommandContribution {
+  description?: string;
+  icon?: string;
+  name: string;
+  options?: PluginApiSlashCommandOption[];
+  run: (context: PluginApiSlashCommandContext) => Promise<void> | void;
+  scope?: PluginApiSlashCommandScope;
+}
+```
+
+| Method                              | Capability     | Description                                                          |
+| ----------------------------------- | -------------- | ------------------------------------------------------------------- |
+| `commands.register(id, command)`    | `ui.commands`  | Registers a `/` slash command for the chat composer.               |
+| `commands.list()`                   | `ui.commands`  | Lists every slash command currently registered across all plugins. |
+
+```ts
+context.subscriptions.push(
+  api.commands.register('shout', {
+    description: 'Shout a message in uppercase',
+    icon: '📢',
+    name: 'shout',
+    options: [{ name: 'message', required: true, type: 'rest' }],
+    run: (slash) => api.messages.send(slash.args.message.toUpperCase()),
+    scope: 'server'
+  })
+);
+```
+
 ## Context and Logger
 
 | Method                         | Capability | Description                                                                |