fix(release): skip pyproject.toml without a static project version

A pyproject.toml that holds only tool config (no [project] table) or lists "version" in [project].dynamic now prints an INFO line and is skipped, like a missing file. A [project] table with neither a version nor a dynamic entry still raises.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/pkgmgr/actions/release/files/pyproject.py

@@ -3,6 +3,11 @@ from __future__ import annotations
 import os
 import re
 
+try:
+    import tomllib
+except ImportError:
+    import tomli as tomllib  # type: ignore
+
 
 def update_pyproject_version(
     pyproject_path: str, new_version: str, preview: bool = False
@@ -18,6 +23,11 @@ def update_pyproject_version(
         print(f"[WARN] Could not read pyproject.toml: {exc}")
         return
 
+    project = tomllib.loads(content).get("project")
+    if project is None or "version" in project.get("dynamic", []):
+        print("[INFO] pyproject.toml declares no static version, skipping.")
+        return
+
     m = re.search(r"(?ms)^\s*\[project\]\s*$.*?(?=^\s*\[|\Z)", content)
     if not m:
         raise RuntimeError("Missing [project] section in pyproject.toml")