feat: Add CoverageFirstSelector for multi-asset coin selection

[jinglescode]

Summary

Adds CoverageFirstSelector - a new coin selection algorithm optimized for complex multi-asset transactions. This two-phase algorithm prioritizes asset type coverage before magnitude optimization, typically resulting in fewer UTxOs selected compared to largest-first when dealing with multi-asset transactions.

Algorithm Overview

Phase 1 (Coverage): Selects UTxOs that maximize asset type coverage reduction using the rating formula:

rating = typesReduced + (intersection / 10)

Exits when ≤1 asset type remains in the deficit.

Phase 2 (Magnitude): Selects UTxOs by magnitude - picking the UTxO with the maximum quantity of each remaining target asset until the deficit is satisfied.

New Exports

import { CoverageFirstSelector, CoinSelectionError } from "@meshsdk/transaction";

const txBuilder = new MeshTxBuilder({
  fetcher: myFetcher,
  selector: new CoverageFirstSelector(),
});

Files Changed

File	Change
coverage-first-selector.ts	New 661-line implementation
coverage-first.test.ts	New 22 comprehensive test cases
coin-selection/index.ts	Added exports
src/index.ts	Added package-level exports

Test Results

Test Suites: 4 passed, 4 total
Tests:       57 passed, 57 total

├── coverage-first.test.ts     22 tests ✓
├── largest-first.test.ts      13 tests ✓  (unchanged)
├── random-improve.test.ts     ✓  (unchanged)
└── cardano-sdk-adapter.test.ts ✓  (unchanged)

Test Categories

• A. Basic Selection (4 tests): Simple transfers, minting, multiple outputs
• B. Coverage Phase (5 tests): Multi-asset preference, rating formula, phase exit conditions
• C. Magnitude Phase (3 tests): Max selection, asset ordering, phase transitions
• D. Error Handling (4 tests): Phase-aware errors with deficit tracking
• E. Edge Cases (6 tests): Min ADA, consolidation, splitting, 10K UTxO performance

Test plan

• All 22 new CoverageFirstSelector tests pass
• All 13 existing LargestFirst tests still pass
• TypeScript compilation succeeds
• 10,000 UTxO performance test completes successfully
• Manual testing with real wallet