Drop Python 3.9 support and modernize macOS runners (#193)

* Drop Python 3.9 support, require Python 3.10+

Python 3.9 reached end-of-life and the codebase uses PEP 604 union
type syntax (str | None) which requires Python 3.10+.

Changes:
- Remove Python 3.9 from CI build matrix
- Update requires-python to >=3.10 in all pyproject.toml files
- Update classifiers to reflect supported Python versions (3.10-3.13)

* Remove macos-13 from CI build matrix

GitHub Actions deprecated macos-13 runner (brownout started Sept 2025,
fully retired Dec 2025). See: https://github.blog/changelog/2025-09-19-github-actions-macos-13-runner-image-is-closing-down/

* Add macos-15-large for Intel Mac builds

Replace deprecated macos-13 with macos-15-large (x86_64 Intel)
to continue supporting Intel Mac users.

* Set MACOSX_DEPLOYMENT_TARGET=13.x for Intel builds

Intel Mac wheels (macos-15-large) now target macOS 13.0/13.3 for
backward compatibility, allowing macOS 13/14/15 Intel users to
install pre-built wheels.

* Remove Intel Mac builds (macos-15-large requires paid plan)

Intel Mac users can build from source. This avoids:
- Paid GitHub Actions runners (macos-15-large)
- Complex cross-compilation setup

* Add macos-15-intel for Intel Mac builds (free runner)

Use macos-15-intel (free standard runner) instead of macos-15-large
(paid). This provides Intel Mac wheel support until Aug 2027.

- MACOSX_DEPLOYMENT_TARGET=13.0 for backward compatibility
- Replaces deprecated macos-13 runner

* Add macOS 26 (beta) to build matrix

Add macos-26 (arm64) runner to the build matrix for testing future
macOS compatibility. This is currently a beta runner that helps ensure
wheels work on upcoming macOS versions.

* Fix macos-15-intel deployment target

The macos-15-intel runner runs macOS 15.7, so Homebrew libraries are
built for macOS 14+. Setting MACOSX_DEPLOYMENT_TARGET=13.0 causes
delocate to fail because system libraries require newer macOS.

Fix by setting deployment target to 15.0 for macos-15-intel, matching
the actual OS version. Intel Mac users will need macOS 15+.

* Exclude macos-15-intel + Python 3.13 (no PyTorch wheels available)

packages/leann-core/pyproject.toml

@@ -7,7 +7,7 @@ name = "leann-core"
 version = "0.3.5"
 description = "Core API and plugin system for LEANN"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = { text = "MIT" }
 
 # All required dependencies included

packages/leann/pyproject.toml

@@ -7,7 +7,7 @@ name = "leann"
 version = "0.3.5"
 description = "LEANN - The smallest vector index in the world. RAG Everything with LEANN!"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = { text = "MIT" }
 authors = [
     { name = "LEANN Team" }
@@ -18,10 +18,10 @@ classifiers = [
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
 ]
 
 # Default installation: core + hnsw + diskann