fix(flow): separate dynamic loop divergence from infinite loops

[lewis6991]

Summary

• split runtime-dependent loop divergence from proven infinite loops in return-flow analysis
• keep MissingReturn fallthrough-friendly for dynamic while and repeat loops when a later return is still reachable
• rename the helper to does_func_body_satisfy_missing_return so the API matches the softer diagnostic contract

Testing

• cargo test -p emmylua_code_analysis check_return_count_test -- --nocapture
• cargo test -p emmylua_code_analysis

[gemini-code-assist]

Code Review

This pull request refactors the return flow analysis for Lua functions by introducing a more granular distinction between proven infinite loops (is_infinite) and runtime-dependent divergence (may_diverge). It renames several fields and functions to better reflect their purpose in the diagnostic pipeline, specifically for the MissingReturn check. The review feedback highlights that loops with constant conditions (e.g., while true) should not be marked as strictly infinite if they contain a break statement, as this could lead to false positives in reachability analysis.

[lewis6991]

/gemini review

[gemini-code-assist]

Code Review

This pull request refactors the return flow analysis in the Lua code analyzer to better distinguish between code that falls through, proven infinite loops, and runtime-dependent divergence. Key changes include renaming can_continue to can_fall_through and can_stall to is_infinite, as well as introducing a may_diverge flag. The MissingReturn diagnostic was updated to utilize these more granular flags, allowing for more accurate detection of missing return statements in functions containing loops. Additionally, several unit tests were added to verify the improved analysis logic. I have no feedback to provide as there were no review comments to evaluate.