fix: standings entries store final match W/D/L for every round

[Rathoz]

Summary

• carryData.match in StandingsParser.parse was a single shared table that every per-round entry stored by reference (match = carryData.match). This meant (a) every standingsentry row carried the final cumulative W/D/L regardless of roundindex, and (b) since placements are computed after all entries are built, match-based tiebreakers (matchdiff — the default Swiss tiebreaker — matchwins, matchwinrate, Buchholz) computed intermediate-round placements from end-of-tournament records.
• The fix snapshots the accumulator per round with Table.copy(carryData.match) at the point the entry is constructed. carryData.match itself continues to accumulate as before; only the stored snapshot per entry is now independent.
• Reviewer note: Final-round entries are unchanged (final cumulative = final cumulative), so definitestatus and final standings are untouched. Intermediate-round stored rows and mid-tournament placements decided by match-based tiebreakers will change on re-render — that is the fix. This PR is based on standings-tests-ai (PR test: add integration tests for standings #7647); the test that asserted the old shared-table behaviour is updated here.

How did you test this change?

• Ran the full busted test suite (605 successes / 0 failures / 0 errors / 0 pending) against the updated code.
• Ran luacheck on both changed files with 0 warnings / 0 errors.
• Updated the test accumulates match scoreboard across rounds in lua/spec/standings_parser_spec.lua: round 1 entry now asserts {w = 1, d = 0, l = 0} (snapshot at end of round 1) and round 2 asserts {w = 1, d = 1, l = 1} (cumulative after round 2); the obsolete comment describing the shared-table behaviour was removed.

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