fix(vtable): align frame border with short frozen rows

[fangsmile]

Summary

• Align the table frame border with the actual bottom frozen row position for short-content list tables.
• Keep previous bottom frozen positioning behavior intact after final layout adjustment.
• Add a local debug demo and regression test for issue [Bug] 数据不足一屏时，设置冻结行，外边框显示不对 #5277.

Test plan

• Verified local demo issue-5277-frozen-row-border: tableGroupHeight=280, bottomFrozenBottom=280, borderHeight=281.
• Verified existing bottom frozen scenarios still pass runtime assertions, including short body, empty body under header, and right frozen body placement.
• Added BugServer photo case for [Bug] 数据不足一屏时，设置冻结行，外边框显示不对 #5277: https://bugserver.cn.goofy.app/case?product=VTable&fileid=6a83c8713335650068dcf413
• Added BugServer photo case for bottom frozen short content: https://bugserver.cn.goofy.app/case?product=VTable&fileid=6a83c88f652957005d019ab2
• Commit hooks passed: rush lint-staged and rush commitlint.
• Focused Jest is blocked by workspace resolution for @visactor/vtable-editors.
• Pre-push rush test --only tag:package is blocked by unrelated package resolution/formula test failures; pushed with --no-verify after maintainer confirmation.

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