fix: correct ADCP_VERSION packaging for PyPI (#85)

* fix: package ADCP_VERSION file correctly for PyPI distribution

Previously, get_adcp_version() returned "v1" (fallback) when installed
from PyPI because ADCP_VERSION was packaged in the wrong location
(adcp-2.12.0.data/data/) and couldn't be found at runtime.

Changes:
- Move ADCP_VERSION into src/adcp/ package directory
- Update pyproject.toml to include it as package data
- Update get_adcp_version() to read from package location
- Remove "v1" fallback to fail fast if file is missing

Now returns "2.5.0" correctly when installed from PyPI.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor: use importlib.resources for ADCP_VERSION file access

Switch from Path(__file__) to importlib.resources.files() for more
robust package data access across different installation methods
(editable installs, zip imports, etc.).

This is the modern, recommended way to access package data files
in Python 3.9+.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: bokelley

pyproject.toml

@@ -61,14 +61,7 @@ Issues = "https://github.com/adcontextprotocol/adcp-client-python/issues"
 where = ["src"]
 
 [tool.setuptools.package-data]
-adcp = ["py.typed"]
-
-# Include ADCP_VERSION file in package
-[tool.setuptools]
-include-package-data = true
-
-[tool.setuptools.data-files]
-"." = ["ADCP_VERSION"]
+adcp = ["py.typed", "ADCP_VERSION"]
 
 [tool.black]
 line-length = 100

ADCP_VERSION renamed to src/adcp/ADCP_VERSION

@@ -191,15 +191,16 @@ def get_adcp_version() -> str:
     of the AdCP specification.
 
     Returns:
-        AdCP specification version (e.g., "v1", "v2")
+        AdCP specification version (e.g., "2.5.0")
+
+    Raises:
+        FileNotFoundError: If ADCP_VERSION file is missing from package
     """
-    from pathlib import Path
+    from importlib.resources import files
 
-    # Read from ADCP_VERSION file at project root
-    version_file = Path(__file__).parent.parent.parent / "ADCP_VERSION"
-    if version_file.exists():
-        return version_file.read_text().strip()
-    return "v1"  # Fallback
+    # Read from ADCP_VERSION file in package
+    version_file = files("adcp") / "ADCP_VERSION"
+    return version_file.read_text().strip()
 
 __all__ = [
     # Version functions