fix: parse current DEX event layouts

[0xfnzero]

Summary

• add current Meteora DLMM event-CPI parsing with legacy compatibility
• update Raydium CPMM/AMM V4 and Orca Whirlpool layouts
• make CPI merging and log/instruction deduplication occurrence-aware
• resolve program discriminator collisions with program-scoped routing
• add reusable 2026-08-13 mainnet fixtures for Meteora, Pump, Raydium, and Orca

Validation

• npm test: 87 passed, 8 opt-in mainnet tests skipped by default
• RUN_MAINNET_TESTS=1 npm test -- --run src/current_mainnet_transactions.test.ts: 8 passed
• npm run check:migration
• TypeScript build passed
• git diff --check

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[0xfnzero]

Superseded by #2, which uses a neutral branch name without the codex prefix.