fix: show builtin syntax kind docs for antiquotation kinds

[alok]

This PR makes hover/go-to-definition on antiquotation kind names (e.g. :str, :num, :term) resolve to the corresponding builtin kind/category declarations, so the editor shows the builtin docstrings.

Changes:

• map antiquotation kind names to builtin kind/category declarations during quotation elaboration
• document builtin syntax node kinds and parser categories
• add a lean/run test exercising builtin syntax kind hover paths

Testing:

• make -j -C build/release
• cd tests/lean/run && ./test_single.sh hover_builtin_syntax_kinds.lean