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/07-context-files.ts

@@ -0,0 +1,36 @@
+/**
+ * Context Files (AGENTS.md)
+ *
+ * Context files provide project-specific instructions loaded into the system prompt.
+ */
+
+import { createAgentSession, discoverContextFiles, SessionManager } from "../../src/index.js";
+
+// Discover AGENTS.md files walking up from cwd
+const discovered = discoverContextFiles();
+console.log("Discovered context files:");
+for (const file of discovered) {
+	console.log(`  - ${file.path} (${file.content.length} chars)`);
+}
+
+// Use custom context files
+const { session } = await createAgentSession({
+	contextFiles: [
+		...discovered,
+		{
+			path: "/virtual/AGENTS.md",
+			content: `# Project Guidelines
+
+## Code Style
+- Use TypeScript strict mode
+- No any types
+- Prefer const over let`,
+		},
+	],
+	sessionManager: SessionManager.inMemory(),
+});
+
+console.log(`Session created with ${discovered.length + 1} context files`);
+
+// Disable context files:
+// contextFiles: []