Add completion spec: uv

Add comprehensive command completion support for uv, the extremely fast
Python package manager by Astral. Includes:

- Full JSON spec covering all subcommands: run, init, add, remove, sync,
  lock, export, tree, version, format, audit, tool (run/install/upgrade/
  list/uninstall/update-shell/dir), python (list/install/find/pin/dir/
  uninstall), pip (compile/sync/install/uninstall/freeze/list/show/tree/
  check), venv, build, publish, cache (clean/prune/dir/size), self
  (update), auth (login/logout/token/dir), generate-shell-completion, help

- 5 Rust generators for dynamic completions:
  - installed_tools: lists tools installed via uv tool
  - project_dependencies: parses pyproject.toml for project deps
  - pip_installed_packages: lists pip-installed packages
  - python_versions: lists installed Python versions
  - installed_pythons: lists managed Python versions for uninstall

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: oz-agent