Add the puga command and plan pull; document the UI plan workflow

- pyproject.toml + puga/cli.py: `pip install -e .` installs a `puga <tool>` command, so no
  venv path is needed (replaces requirements.txt)
- tools/plan_push.py: `pull <uuid>` reads a plan (incl. UI edits) back into a YAML spec;
  recipe entries may carry an amount so switched-off recipes round trip; fixes a variable
  that overwrote the plan name in build_payload, with a regression test
- README: usage with the puga command, and a section on working on the same plans in the
  PRUNplanner UI and from Claude (write, edit in UI, read back)
- CLAUDE.md updated accordingly

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

puga/cli.py

@@ -0,0 +1,29 @@
+"""`puga <tool> [args]`: run a tool from tools/ (installed as the `puga` command by pip install -e .)."""
+import runpy, sys
+from . import ROOT
+
+ALIASES = {"plan": "plan_push"}
+
+
+def _tools():
+    return sorted(p.stem for p in (ROOT / "tools").glob("*.py"))
+
+
+def main():
+    args = sys.argv[1:]
+    if not args or args[0] in ("-h", "--help", "help"):
+        print("usage: puga <tool> [args]\n\ntools:")
+        for t in _tools():
+            print("  " + ("plan  (plan_push)" if t == "plan_push" else t))
+        print("  test  (run the test suite)")
+        return
+    tool, rest = args[0], args[1:]
+    if tool == "test":
+        import pytest
+        sys.exit(pytest.main(["-q", *rest]))
+    tool = ALIASES.get(tool, tool)
+    path = ROOT / "tools" / f"{tool}.py"
+    if not path.exists():
+        sys.exit(f"unknown tool '{tool}' (try: puga help)")
+    sys.argv = [str(path), *rest]
+    runpy.run_path(str(path), run_name="__main__")