refactor: Introduce shot_*! test macros for snapshot testing

[zharinov]

Summary

• Add shot_bytecode!, shot_cst!, shot_ast!, shot_types!, shot_error! macros in test_utils.rs
• Convert all emit, compile, and grammar tests to use new macros
• Replace inline snapshots with file-based snapshots (106 new snapshot files)

Why

Reduces test boilerplate by embedding indoc! inside macros. Pattern: shot_X!(query) instead of let input = indoc!{...}; let res = Query::expect_X(input); insta::assert_snapshot!(res).