libvcs(__init__, ci) Export __version__; fix docs path filter

why: gp_sphinx.config.make_linkcode_resolve() reads __version__ via
getattr(package_module, "__version__", ""), falling back to "" and
generating broken source-link URLs like blob/v/src/... The docs CI
also never triggered on Python source changes because the paths-filter
used libvcs/** instead of src/libvcs/** (src layout).
what:
- Export __version__ from .__about__ in __init__.py
- Add __version__ to __all__
- Fix paths-filter: libvcs/** -> src/libvcs/**
- Add workflow_dispatch trigger to docs.yml

Author: tony

.github/workflows/docs.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - master
+  workflow_dispatch:
 
 permissions:
   contents: read
@@ -30,7 +31,7 @@ jobs:
               - 'docs/**'
               - 'examples/**'
             python_files:
-              - 'libvcs/**'
+              - 'src/libvcs/**'
               - pyproject.toml
               - uv.lock
 

src/libvcs/__init__.py

@@ -10,7 +10,10 @@
 from .sync.hg import HgSync
 from .sync.svn import SvnSync
 
+from .__about__ import __version__
+
 __all__ = [
+    "__version__",
     "BaseSync",
     "CmdLoggingAdapter",
     "GitSync",