chore (tree-sitter-xpath): Remove “E2E” tests

These early tests were intended to demonstrate using the parser, in a way that relates to concepts we’d build later in the project exploration. Specifically, they demonstrated querying aspects of the parsed syntax tree to identify path sub-expressions.

They have probably not had much value for quite a while, as we’ve had real logic doing this quite differently. This is especially obvious now, as of #166, where we have substantially matured that approach.

This leaves standard tree-sitter testing intact, which is more than sufficient for validating the parser grammar’s **syntax tree output**. All other XPath-related logic is tested much more thoroughly downstream (including quite a bit exercising the grammar, both in `xpath` and `xforms-engine` packages).

Small note that this also moves type tests before the standard tree-sitter tests. This is probably a change we won’t want to make in other packages, at least without some additional consideration. It makes sense here because there’s no downstream testing that relies on evaluating TypeScript source modules. In other packages, type tests failing early would prevent further test tasks from running (which would be great in CI, but probably quite annoying in dev).