Rename Gadget CLI to Tangle CLI

[shekohex]

Fixes #225

Rename the Gadget CLI to Tangle CLI and update subcommands.

• cli/Cargo.toml

  • Rename the package from cargo-gadget to cargo-tangle.

• cli/src/main.rs

  • Update the bin_name attribute in the clap macro to cargo-tangle.
  • Add a new subcommand Gadget to the Commands enum.
  • Move the Create and Deploy subcommands under the Gadget subcommand.

---

For more details, open the Copilot Workspace session.