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>

pyproject.toml

@@ -0,0 +1,19 @@
+[build-system]
+requires = ["setuptools>=61"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "puga"
+version = "0.1.0"
+description = "Tools and know-how for Claude to assist in Prosperous Universe"
+requires-python = ">=3.12"
+dependencies = ["pyyaml"]
+
+[project.optional-dependencies]
+dev = ["pytest"]
+
+[project.scripts]
+puga = "puga.cli:main"
+
+[tool.setuptools]
+packages = ["puga"]