fix: bound keyurl caches with FIFO eviction to prevent memory leak

[luchobonatti]

Closes zama-ai#336

Summary

• Bound keyurlCache in networkV1.ts (v1 only) and privateKeyurlCache in AbstractRelayerProvider.ts (v1 + v2) to MAX_KEYURL_CACHE_SIZE = 16 entries
• FIFO eviction via Map insertion order — when the 17th unique relayer URL is inserted, the oldest entry is dropped
• Zero new dependencies — uses Map.keys().next().value! which is O(1) and guaranteed by ES2015+
• Export _clearKeyurlCache() from networkV1.ts for test isolation, mirroring the existing _clearTFHEPkeParamsCache() pattern

Changes

File	Change
src/relayer-provider/v1/networkV1.ts	Record → bounded Map, MAX_KEYURL_CACHE_SIZE = 16, FIFO eviction, export _clearKeyurlCache()
src/relayer-provider/AbstractRelayerProvider.ts	MAX_KEYURL_CACHE_SIZE = 16, FIFO eviction block before privateKeyurlCache.set()
src/relayer-provider/v1/networkV1.test.ts	Cache hit test + FIFO eviction test (17 URLs), beforeEach/afterEach isolation hooks
src/relayer-provider/v2/RelayerV2Provider_keyurl.test.ts	FIFO eviction test (17 providers)

Test plan

• tsc --noEmit passes
• 23 tests pass across both affected suites
• Full suite: 1376/1384 tests pass, 8 skipped (pre-existing), 0 failures

[Copilot]

Pull request overview

Bounds relayer key URL/TFHE parameter caches to prevent unbounded growth (memory leak) by introducing FIFO eviction at a fixed maximum size, plus adds tests to validate cache hits and eviction behavior.

Changes:

• Replace the v1 keyurlCache Record with a bounded Map (max 16) using FIFO eviction and add _clearKeyurlCache() for test isolation.
• Add FIFO eviction (max 16) to the shared privateKeyurlCache used by AbstractRelayerProvider (applies to v1 + v2).
• Add/extend tests for cache hits and FIFO eviction in both v1 and v2 suites.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/relayer-provider/v2/RelayerV2Provider_keyurl.test.ts	Adds a FIFO eviction test validating the 17th unique provider triggers eviction and a refetch causes an additional fetch.
src/relayer-provider/v1/networkV1.ts	Introduces bounded Map cache with FIFO eviction and exports _clearKeyurlCache() for tests.
src/relayer-provider/v1/networkV1.test.ts	Adds cache-hit and FIFO-eviction tests and clears cache/routes between tests for isolation.
src/relayer-provider/AbstractRelayerProvider.ts	Adds FIFO eviction to the promise cache for TFHEPkeParams to bound memory usage across relayer URLs.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

MAX_KEYURL_CACHE_SIZE is duplicated here and in AbstractRelayerProvider.ts (kept in sync via comments). Consider extracting it to a shared constant (single source of truth) to avoid the two caches silently diverging in size in future edits.

[Copilot]

MAX_KEYURL_CACHE_SIZE is defined here and duplicated in v1/networkV1.ts. Consider moving this to a shared constant (or exporting/importing one value) to prevent future drift between v1 and v2 cache bounds.

Suggested change

	// Bounded to MAX_KEYURL_CACHE_SIZE with FIFO eviction. Mirrors networkV1.ts.
	const MAX_KEYURL_CACHE_SIZE = 16;
	// Shared cache bound for relayer key-url caching. Other implementations
	// should import/export this value rather than redefining it.
	export const MAX_KEYURL_CACHE_SIZE = 16;