feat: add skills system, hooks integration, and OpenAI-compatible provider

- Add skill system with types, registry, SkillTool, and 5 bundled skills
  (simplify, commit, review, debug, test)
- Integrate hooks into QueryEngine at 9 lifecycle points (SessionStart,
  UserPromptSubmit, PreToolUse, PostToolUse, PostToolUseFailure,
  PreCompact, PostCompact, Stop, SessionEnd)
- Add LLM provider abstraction supporting both Anthropic Messages API
  and OpenAI Chat Completions API (works with GPT, DeepSeek, Qwen, etc.)
- Add CODEANY_API_TYPE env var ('anthropic-messages' | 'openai-completions')
  with auto-detection from model name
- Remove all ANTHROPIC_* env var references, only support CODEANY_* prefix
- Add model pricing and context windows for OpenAI/DeepSeek models
- Remove direct @anthropic-ai/sdk dependency from all files except the
  Anthropic provider (types.ts, engine.ts, etc. are now provider-agnostic)
- Add PermissionBehavior type export
- Bump version to 0.2.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/skills/index.ts

@@ -0,0 +1,25 @@
+/**
+ * Skills Module - Public API
+ */
+
+// Types
+export type {
+  SkillDefinition,
+  SkillContentBlock,
+  SkillResult,
+} from './types.js'
+
+// Registry
+export {
+  registerSkill,
+  getSkill,
+  getAllSkills,
+  getUserInvocableSkills,
+  hasSkill,
+  unregisterSkill,
+  clearSkills,
+  formatSkillsForPrompt,
+} from './registry.js'
+
+// Bundled skills
+export { initBundledSkills } from './bundled/index.js'