feat: Add graph partition support for DiskANN backend

- Add GraphPartitioner class for advanced graph partitioning
- Add partition_graph_simple function for easy-to-use partitioning
- Add pybind11 dependency for C++ executable building
- Update __init__.py to export partition functions
- Include test scripts for partition functionality

The partition functionality allows optimizing disk-based indices
for better search performance and memory efficiency.

uv.lock

@@ -2281,6 +2281,7 @@ dependencies = [
     { name = "pdfplumber" },
     { name = "protobuf" },
     { name = "psutil" },
+    { name = "pybind11" },
     { name = "pymupdf" },
     { name = "pypdf2" },
     { name = "pypdfium2" },
@@ -2360,6 +2361,7 @@ requires-dist = [
     { name = "pre-commit", marker = "extra == 'dev'", specifier = ">=3.5.0" },
     { name = "protobuf", specifier = "==4.25.3" },
     { name = "psutil", specifier = ">=5.8.0" },
+    { name = "pybind11", specifier = ">=3.0.0" },
     { name = "pymupdf", specifier = ">=1.26.0" },
     { name = "pypdf2", specifier = ">=3.0.0" },
     { name = "pypdfium2", specifier = ">=4.30.0" },
@@ -4203,6 +4205,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/10/15/6b30e77872012bbfe8265d42a01d5b3c17ef0ac0f2fae531ad91b6a6c02e/pyarrow-21.0.0-cp39-cp39-win_amd64.whl", hash = "sha256:cdc4c17afda4dab2a9c0b79148a43a7f4e1094916b3e18d8975bfd6d6d52241f", size = 26227521, upload-time = "2025-07-18T00:57:29.119Z" },
 ]
 
+[[package]]
+name = "pybind11"
+version = "3.0.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/ef/83/698d120e257a116f2472c710932023ad779409adf2734d2e940f34eea2c5/pybind11-3.0.0.tar.gz", hash = "sha256:c3f07bce3ada51c3e4b76badfa85df11688d12c46111f9d242bc5c9415af7862", size = 544819, upload-time = "2025-07-10T16:52:09.335Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/41/9c/85f50a5476832c3efc67b6d7997808388236ae4754bf53e1749b3bc27577/pybind11-3.0.0-py3-none-any.whl", hash = "sha256:7c5cac504da5a701b5163f0e6a7ba736c713a096a5378383c5b4b064b753f607", size = 292118, upload-time = "2025-07-10T16:52:07.828Z" },
+]
+
 [[package]]
 name = "pycparser"
 version = "2.22"