Creates the player_meta table (gogobee_legacy_migration.md §2.1) with the
three columns L2 needs: arena_wins, arena_losses, invasion_score. Future
phases ALTER in their own columns. Naming follows the §2.0 callout — no
dnd_ prefix on new tables.
Helpers in internal/plugin/player_meta.go: loadPlayerMeta,
upsertPlayerMetaArena, backfillPlayerMetaArena (INSERT OR IGNORE,
idempotent, logs row count per Phase R1 precedent). Plugin Init runs
the backfill once on startup.
Dual-write per §11: every char.ArenaWins++/ArenaLosses++ in
adventure_arena.go also calls upsertPlayerMetaArena. AdvCharacter
columns stay in place — reads will switch back to AdvCharacter trivially
if a rollback is needed before L5 teardown.
Read swap: handleArenaStats and renderDnDSheet now load player_meta and
prefer its values (falling back to AdvCharacter if the row is missing,
which only matters during the deploy window before backfill runs).
renderArenaPersonalStats's signature changed from (char, stats) to
(displayName, wins, losses, stats) so the render is DB-free.
Tests: TestPlayerMetaArenaBackfill_Idempotent verifies double-run
backfill is a no-op and doesn't clobber post-backfill dual-writes;
TestUpsertPlayerMetaArena_RoundTrip covers insert/update/missing-user
paths.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
