test: add core API coverage for translation registry

[ScriptedBro]

Add comprehensive test suite for Translation Registry core API

Closes #382

Summary

Adds lib/translator/tests/registry.test.ts with 29 tests covering the core public API of the Translation Registry — the most critical module in the project. Achieves 90.97% line coverage on lib/translator/registry.ts as measured by vitest --coverage.

What changed

• New file: lib/translator/tests/registry.test.ts (29 tests, 641 lines)
• Dependencies: Added @vitest/coverage-v8@3.2.7 for coverage reporting

Test coverage

Area	Tests	What's covered
translateEvent	5	Known SAC transfer, unregistered contract fallback, blueprint matches rejection, blueprint translate returning null
translateEvents	3	Mixed batch processing, property-based robustness (never throws on any input shape), error handling via translateEventSafe catch block
translateWithCache	6	Redis hit returns cached result, Redis miss triggers store, persisted fields with defined status, persisted fields with default status, skip caching when txHash/id missing, skip when Redis disabled
registerBlueprint	2	New contract becomes translatable, merging second schema with ledger-based selection
registerUpgrade	3	New schema selected for post-upgrade ledgers, old schema for pre-upgrade, cache cleared only for the upgraded contract, no-op for unregistered contracts
matchesEventCriteria	7	contractId match, topic equals (exact), topic includes (case-insensitive), topic decodedName, combined criteria, empty criteria, out-of-range topic index
Registry helpers	4	hasBlueprint, getRegisteredContracts, getBlueprintCount

Coverage results

 % Coverage report from v8
 File         | % Stmts | % Branch | % Funcs | % Lines
 registry.ts  |   90.97 |    75.35 |   92.30 |   90.97

Verification

• All 29 new tests pass
• All 8 existing registry tests pass (registry.fallback.test.ts, registry.resolution-cache.test.ts, registry.versioning.test.ts)
• 37/37 tests green

Uncovered lines (8.93%)

• Lines 400, 408: console.warn inside the blueprint null-check branch (defensive unreachable — schema.blueprint is always set by resolveSchema)
• Lines 418-428: unknownEventNoBlueprintApplicable path (requires a schema with a null blueprint, which cannot occur via buildRegistry or registerBlueprint)
• Line 617: Array.isArray(existing) guard in registerBlueprint (defensive branch — REGISTRY is typed as Map<string, ContractRegistryEntry>, never stores arrays)