Fix gold detection reliability and diagnostics

[azumag]

Summary

• capture Best Segments cumulative snapshots before each split, keyed by split index
• restore snapshots from the saved .lss file after restarts or missed polls; segment durations are converted to cumulative values and incomplete histories are rejected
• read LiveSplit state in one TCP session per poll to reduce state races and process churn
• surface missing OBS settings and polling/file-parse errors in debug diagnostics

Verification

• git diff --check
• extracted and parsed the embedded PowerShell payload, then verified duration-to-cumulative conversion against a sample .lss fixture
• Windows Release Build succeeded for head commit 807ecad: https://github.com/azumag/LiveSplitGoldAlert/actions/runs/32610702716
• runtime validation still needs LiveSplit + OBS on Windows.