Get rid of ziggy-pydust dependency

[recipe]

• The binding layer is now a plain C-ABI shared library driven by stdlib ctypes.
• Bumped zig version to 0.16.0.
• Start using Hatch for the build. Poetry is gone entirely. Since uv's own build backend can't run custom build steps (by design - no native extension support), the backend is now hatchling with a custom build hook, and uv is the frontend for everything.
• Fixed an unbounded memory retention in streaming mode
• Fixed: Concurrent use of one StreamWrapper is memory-unsafe
• Fixed trie memory amplification with the Adaptive Radix Tree (ART) node-classing idea:
  Three types of nodes:
  • one — a single (key, id) pair stored inline in the node, zero heap allocation, lookup is one byte compare. Covers ~99% of nodes (including leaves as none).
  • few — up to 16 children in a heap side-array, looked up with a branchless 16-byte SIMD compare
  • dense — a direct-indexed 256-entry table for the rare hubs (root, some depth-1 nodes), upgraded automatically on the 17th child.