test: add TTL cache behavior tests for tick size validation

[Aboudjem]

Summary

• Adds 5 tests covering the tick size cache TTL behavior introduced in fix: tick size #299
• Validates the exact regression scenario from The new tick size validation fails if a previous createOrder request used a larger tick size. #265 (cached 0.01 → updated 0.001 after TTL expiry)
• Tests clearTickSizeCache for both per-token and full cache invalidation

Tests added

1. Returns cached value within TTL without refetching
2. Refetches after TTL expires
3. Picks up updated tick size after TTL expires (the The new tick size validation fails if a previous createOrder request used a larger tick size. #265 regression)
4. clearTickSizeCache forces refetch for specific token
5. clearTickSizeCache with no arg clears all tokens

Test plan

• pnpm typecheck — clean
• pnpm test — 179/179 pass
• New tests: 5/5 pass in 15ms

Relates to #265

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Note

Low Risk
Low risk: adds isolated unit tests only, exercising existing tick size caching/TTL and clearTickSizeCache behavior without changing production logic.

Overview
Adds a new tick-size-cache.test.ts suite that verifies ClobClient.getTickSize respects the tick-size cache TTL (no refetch within TTL, refetch and value update after expiry).

Also adds coverage for clearTickSizeCache, asserting both per-token and full-cache invalidation force subsequent refetches.

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