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/04-skills.ts

@@ -0,0 +1,44 @@
+/**
+ * Skills Configuration
+ *
+ * Skills provide specialized instructions loaded into the system prompt.
+ * Discover, filter, merge, or replace them.
+ */
+
+import { createAgentSession, discoverSkills, SessionManager, type Skill } from "../../src/index.js";
+
+// Discover all skills from cwd/.pi/skills, ~/.pi/agent/skills, etc.
+const allSkills = discoverSkills();
+console.log(
+	"Discovered skills:",
+	allSkills.map((s) => s.name),
+);
+
+// Filter to specific skills
+const filteredSkills = allSkills.filter((s) => s.name.includes("browser") || s.name.includes("search"));
+
+// Or define custom skills inline
+const customSkill: Skill = {
+	name: "my-skill",
+	description: "Custom project instructions",
+	filePath: "/virtual/SKILL.md",
+	baseDir: "/virtual",
+	source: "custom",
+};
+
+// Use filtered + custom skills
+const { session } = await createAgentSession({
+	skills: [...filteredSkills, customSkill],
+	sessionManager: SessionManager.inMemory(),
+});
+
+console.log(`Session created with ${filteredSkills.length + 1} skills`);
+
+// To disable all skills:
+// skills: []
+
+// To use discovery with filtering via settings:
+// discoverSkills(process.cwd(), undefined, {
+//   ignoredSkills: ["browser-tools"],  // glob patterns to exclude
+//   includeSkills: ["brave-*"],        // glob patterns to include (empty = all)
+// })