Channel lazy load: discover_enabled() only imports enabled channel
modules instead of all 18 modules with heavy SDKs (telegram, discord,
slack, etc). discover_all() now delegates to discover_enabled().
Lazy OpenAI client: defer AsyncOpenAI() + httpx construction to
_ensure_client() with asyncio.Lock double-checked locking. openai
and httpx imports moved from module-level into _ensure_client().
Minor: lazy Nanobot/RunResult and CronService exports via __getattr__.
Benchmark: 6910ms → 460ms (-93.3%)
Keep importlib.metadata as the primary source for installed packages, but avoid PackageNotFoundError when nanobot is imported directly from a source tree.
Made-with: Cursor
Fixes#2856
Previously __version__ was hardcoded as '0.4.1' in __init__.py while
pyproject.toml declared version '0.1.5'. This caused nanobot gateway to
report version 0.4.1 on startup while pip showed 0.1.5.
Now __version__ reads from importlib.metadata.version('nanobot-ai'),
keeping pyproject.toml as the single source of truth.
