Add SDK usage examples

12 examples showing increasing levels of customization:
- 01-minimal: all defaults
- 02-custom-model: model and thinking level
- 03-custom-prompt: replace or modify prompt
- 04-skills: discover, filter, merge skills
- 05-tools: built-in tools, custom tools
- 06-hooks: logging, blocking, result modification
- 07-context-files: AGENTS.md files
- 08-slash-commands: file-based commands
- 09-api-keys-and-oauth: API key resolution, OAuth config
- 10-settings: compaction, retry, terminal settings
- 11-sessions: persistence options
- 12-full-control: replace everything

Also exports FileSlashCommand type from index.ts

packages/coding-agent/examples/sdk/08-slash-commands.ts

@@ -0,0 +1,37 @@
+/**
+ * Slash Commands
+ *
+ * File-based commands that inject content when invoked with /commandname.
+ */
+
+import { createAgentSession, discoverSlashCommands, SessionManager, type FileSlashCommand } from "../../src/index.js";
+
+// Discover commands from cwd/.pi/commands/ and ~/.pi/agent/commands/
+const discovered = discoverSlashCommands();
+console.log("Discovered slash commands:");
+for (const cmd of discovered) {
+	console.log(`  /${cmd.name}: ${cmd.description}`);
+}
+
+// Define custom commands
+const deployCommand: FileSlashCommand = {
+	name: "deploy",
+	description: "Deploy the application",
+	source: "(custom)",
+	content: `# Deploy Instructions
+
+1. Build: npm run build
+2. Test: npm test  
+3. Deploy: npm run deploy`,
+};
+
+// Use discovered + custom commands
+const { session } = await createAgentSession({
+	slashCommands: [...discovered, deployCommand],
+	sessionManager: SessionManager.inMemory(),
+});
+
+console.log(`Session created with ${discovered.length + 1} slash commands`);
+
+// Disable slash commands:
+// slashCommands: []