Migrate exception handling tests from Rust to Ruby integration tests

[dak2]

Motivation

The Rust exception tests in exceptions.rs were largely full-pipeline integration tests (parse → install → propagate → run_all) that duplicated coverage already provided by Ruby integration tests in test/exception_test.rb. This is part of the ongoing effort to consolidate integration-level testing in the Ruby test suite and keep only true unit tests on the Rust side.

Changes

Rust side (core/src/analyzer/exceptions.rs):

• Removed 15 redundant integration tests that are already covered by Ruby tests
• Kept 2 true unit tests (test_rescue_variable_scope_restore, test_rescue_variable_scope_removal) that verify internal scope state not accessible via CLI

Ruby side (test/exception_test.rb):

• Added 6 unique test scenarios previously only covered in Rust:
  • test_nested_begin_rescue_union_type — nested begin/rescue returns union of all branches
  • test_begin_ensure_only_no_false_positive — begin/ensure without rescue produces no false positive
  • test_rescue_modifier_same_type_dedup — rescue modifier with same type deduplicates
  • test_ensure_side_effects_no_false_positive — ensure block side effects don't cause false positives
  • test_rescue_qualified_exception_class — qualified exception class (Net::HTTPError) is handled
  • test_empty_rescue_body_returns_nil — empty rescue body infers nil type

Checked

• cd core && cargo test --lib — all Rust tests pass
• bundle exec rake test — all Ruby tests pass

🤖 Generated with Claude Code