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/09-api-keys-and-oauth.ts

@@ -0,0 +1,45 @@
+/**
+ * API Keys and OAuth
+ *
+ * Configure API key resolution. Default checks: models.json, OAuth, env vars.
+ */
+
+import {
+	createAgentSession,
+	configureOAuthStorage,
+	defaultGetApiKey,
+	SessionManager,
+} from "../../src/index.js";
+import { getAgentDir } from "../../src/config.js";
+
+// Default: uses env vars (ANTHROPIC_API_KEY, etc.), OAuth, and models.json
+const { session: defaultSession } = await createAgentSession({
+	sessionManager: SessionManager.inMemory(),
+});
+console.log("Session with default API key resolution");
+
+// Custom resolver
+const { session: customSession } = await createAgentSession({
+	getApiKey: async (model) => {
+		// Custom logic (secrets manager, database, etc.)
+		if (model.provider === "anthropic") {
+			return process.env.MY_ANTHROPIC_KEY;
+		}
+		// Fall back to default
+		return defaultGetApiKey()(model);
+	},
+	sessionManager: SessionManager.inMemory(),
+});
+console.log("Session with custom API key resolver");
+
+// Use OAuth from ~/.pi/agent while customizing everything else
+configureOAuthStorage(getAgentDir()); // Must call before createAgentSession
+
+const { session: hybridSession } = await createAgentSession({
+	agentDir: "/tmp/custom-config", // Custom config location
+	// But OAuth tokens still come from ~/.pi/agent/oauth.json
+	systemPrompt: "You are helpful.",
+	skills: [],
+	sessionManager: SessionManager.inMemory(),
+});
+console.log("Session with OAuth from default location, custom config elsewhere");