Update setup instructions for Cargo config generation

Clarified the process for generating .cargo/config.toml using `cargo run -p xtask -- setup` in both .cargo/README.md and README.md. Updated documentation to reflect the new setup command and its purpose.

.cargo/README.md

@@ -1,3 +1,9 @@
-## Attention
+## Cargo Config
 
-Make sure to execute the `setup-system` script after any modification to `cargo.toml`.
+The `config.toml` file is generated from `config.toml.mustache` by running:
+
+```bash
+cargo run -p xtask -- setup
+```
+
+This file is gitignored because it contains machine-specific paths. After setup, you can use `cargo xtask` for subsequent commands.

README.md

@@ -223,8 +223,7 @@ cd spacedrive
 
 # Install dependencies
 bun install
-cargo install cargo-xtask # (if not already installed)
-cargo xtask setup
+cargo run -p xtask -- setup  # generates .cargo/config.toml with aliases
 
 # Run the desktop app (automatically starts daemon)
 cd apps/tauri