fix(awk): treat # inside regex literals as literal, not comment

[chaliy]

Summary

• The awk normalizer now recognizes regex literals (/pattern/) in both pattern and action contexts
• Previously, regex was only recognized inside { } braces, so /#/ in a pattern position caused # to be treated as a comment start, resulting in "unterminated regex" errors

Test plan

• awk_regex_hash_pattern — /#/ matches lines containing #
• awk_regex_hash_caret — /^#/ matches comment lines
• awk_regex_hash_no_match — non-hash regex still works
• All 119 awk spec tests pass
• All 1748 bash spec tests pass
• cargo fmt --check and cargo clippy clean

Closes #835