Fix docs/script mismatch: replace todo command with actual script invocation

[Copilot]

README and SKILL.md referenced a todo command that doesn't exist — no entry point is registered in pyproject.toml. The actual script is scripts/ms-todo-sync.py, invoked via uv run scripts/ms-todo-sync.py.

Changes

• README.md — Updated all 12 command examples (todo login, todo list, etc.) to uv run scripts/ms-todo-sync.py <subcommand>
• SKILL.md — Updated all 87 command references across the cheat sheet, agent workflow, and full command reference sections
• scripts/ms-todo-sync.py — Updated argparse prog name, epilog example, and two user-facing error messages to reflect the correct invocation

-todo login
-todo add "Buy groceries" -l "Shopping" -p high -d 2
+uv run scripts/ms-todo-sync.py login
+uv run scripts/ms-todo-sync.py add "Buy groceries" -l "Shopping" -p high -d 2

Product name references ("Microsoft To Do"), project/repo name (ms-todo-sync), and Graph API paths (/me/todo/lists) are unchanged.