Add simplex new and simplex example commands, improve generated t…

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…est template, and expand README docs

New commands

simplex new <name>

Creates a complete Simplex project scaffold in a new / directory. Equivalent to running simplex init --lib in a freshly created directory, but with a better UX — errors immediately if the target directory already exists rather than clobbering existing files.

simplex example <name>

Scaffolds a full example project into a new directory. Currently supports simplex example basic, which writes all files from the examples/basic/ template (including the options, option_offer, array_tr_storage, bytes32_tr_storage, and dual_currency_deposit contracts) using include_str! so the content is embedded in the binary at compile time. The Cargo.toml is generated dynamically to pin to the latest published smplx-std version from crates.io, consistent with how simplex new works.

Improved generated test template

The default test file produced by simplex new and simplex init --lib was previously a non-compiling todo!() stub. It is now a working end-to-end p2pk integration test that demonstrates:

• Instantiating a program with typed arguments (P2pkArguments)
• Deriving a script pubkey from the program
• Funding the script via FinalTransaction + PartialOutput
• Spending the script by supplying a P2pkWitness with DUMMY_SIGNATURE and RequiredSignature::Witness so the signer fills in the real signature

The crate name (simplex_<project_name>) is substituted at generation time so the artifact imports resolve correctly for any project name. anyhow is now also added to the generated Cargo.toml to support the -> anyhow::Result<()> return type.

README

• Replaced the cargo add smplx-std getting-started flow with simplex new as the primary entry point
• Added simplex new and simplex example to the CLI command reference
• Added a "Typical workflow" section showing the new -> build -> test flow
• Added a "Using smplx-std as a library" section covering: dependency setup, how generated artifacts are structured, instantiating a program with arguments, funding and spending scripts with FinalTransaction, a key types reference table, and the #[simplex::test] macro
• Updated the future work checklist to mark simplex new and simplex example as complete