✨➖📝 cli, vanth, meta, flake: Simplify dependencies, add meta crate, and improve docs

- Removed dependencies `sqlx` and `bevy_app` to simplify the project.
- Added new crate `vanth_meta` for generating example SVGs.
- Updated CLI tests to use `assert_cmd` for better test assertions.
- Enhanced README with comprehensive library and CLI usage documentation.
- Modified `Store::write` in `vanth` crate to return the content hash.
- Set `checkPhase` to empty in Nix flake configuration.

crates/cli/src/main.rs

@@ -3,6 +3,7 @@ use clap::Parser;
 mod cli;
 
 pub use cli::*;
+use tracing::trace;
 
 fn main() {
     tracing_subscriber::fmt()