Release 0.4.4: async tasks, nested refs, and hash correctness (#22)

• Fix: AsyncClient now awaits async def task functions correctly.
• Fix: function hashes include immutable globals used by nested code objects, plus stable built-ins like range, slice, and datetime values.
• Fix: nested ResultRef / AsyncResultRef values resolve inside containers and input refs are deduplicated in commit metadata.
• Fix: nested ref resolution preserves tuple subclasses and avoids invalid dict/frozenset containers from unhashable resolved values.
• Fix: task functions returning awaitable objects keep those objects as the actual cached result.
• Fix: base installs raise a clear cashet[redis] extra error when Redis backends are imported without Redis dependencies.