chore: auto-generate _version.py via hatch-vcs (#74)

Configure hatch-vcs build hook to generate _version.py from git tags
during build, instead of maintaining a hardcoded placeholder. The file
is now gitignored since it is build-generated.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: georgeh0

.gitignore

@@ -41,5 +41,8 @@ htmlcov/
 .pytest_cache/
 .mypy_cache/
 
+# Generated version file
+src/cocoindex_code/_version.py
+
 # CocoIndex
 .cocoindex_code/

pyproject.toml

@@ -55,6 +55,10 @@ Issues = "https://github.com/cocoindex-io/cocoindex-code/issues"
 
 [tool.hatch.version]
 source = "vcs"
+fallback-version = "999.0.0"
+
+[tool.hatch.build.hooks.vcs]
+version-file = "src/cocoindex_code/_version.py"
 
 [tool.hatch.build.targets.wheel]
 packages = ["src/cocoindex_code"]