fix(python): derive __version__ from package metadata with dev sentinel

The Python SDK hardcoded __version__ = "0.1.0" in copilot/__init__.py and
version = "0.1.0" in pyproject.toml. The publish workflow only rewrites
pyproject.toml at release time, so the public runtime __version__ drifted
and always reported a stale version regardless of what was published.

Derive __version__ from installed package metadata via importlib.metadata,
falling back to a 0.0.0.dev0 sentinel (instead of a real-looking version)
when no metadata is present. Set the committed pyproject.toml version to the
same dev sentinel, matching the .NET and Rust SDKs; CI injects the real
version at publish time.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

python/copilot/__init__.py

@@ -4,6 +4,9 @@
 JSON-RPC based SDK for programmatic control of GitHub Copilot CLI
 """
 
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as _pkg_version
+
 from ._mode import (
     BUILTIN_TOOLS_ISOLATED,
     CopilotClientMode,
@@ -145,7 +148,13 @@
     define_tool,
 )
 
-__version__ = "0.1.0"
+try:
+    __version__ = _pkg_version("github-copilot-sdk")
+except PackageNotFoundError:
+    # No installed package metadata (e.g. running from a source checkout that
+    # was never installed). Use a sentinel that can never masquerade as a real
+    # release rather than a hardcoded version that would silently go stale.
+    __version__ = "0.0.0.dev0"
 
 __all__ = [
     "AutoModeSwitchHandler",

python/pyproject.toml

@@ -4,7 +4,10 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "github-copilot-sdk"
-version = "0.1.0"
+# Placeholder; the real version is injected at publish time (see
+# .github/workflows/publish.yml). Kept as a dev sentinel so source/editable
+# installs never report a stale real version, matching the .NET and Rust SDKs.
+version = "0.0.0.dev0"
 description = "Python SDK for GitHub Copilot CLI"
 readme = "README.md"
 requires-python = ">=3.11"