Fix tree-sitter not found after cargo install

[skabbio1976]

Summary

• Install-TreeSitter does not add ~/.cargo/bin to $env:PATH after cargo install, unlike Install-Rust which does.
• When Rust is already present (so Install-Rust is a no-op) and ~/.cargo/bin is not in the inherited PATH, the tree-sitter binary cannot be found by Export-GrammarBinding.
• Adds the same PATH update logic that Install-Rust already uses.

Repro

Build from Linux where ~/.cargo/bin is not in the shell's default PATH. The build fails with:

Invoke-Expression: The term 'tree-sitter' is not recognized as a name of a cmdlet,
function, script file, or executable program.

Fix

# Ensure cargo bin directory is in PATH so tree-sitter can be found
if (!$IsWindows) {
    $cargoBin = "$env:HOME/.cargo/bin"
    if ($env:PATH -notlike "*$cargoBin*") {
        $env:PATH += ":$cargoBin"
    }
} else {
    $cargoBin = "$env:USERPROFILE\.cargo\bin"
    if ($env:PATH -notlike "*$cargoBin*") {
        $env:PATH += ";$cargoBin"
    }
}

Contact: johan.kallio@teamtech.se for questions.