Add ResourceQuota getter and builder edge case coverage

[sfloess]

Part of #1: Code Coverage Below Threshold

Problem

ResourceQuota getters (getMaxHeapBytes(), getMaxThreadCount(), getMaxCpuTimeNanos()) are never directly asserted in tests. Builder boundary values (zero) are also untested.

Scope

Add tests covering:

• Each getter returns Optional.of(value) when set via builder
• Each getter returns Optional.empty() when not set
• Builder accepts zero values (boundary: maxHeapBytes(0), maxThreadCount(0), maxCpuTimeNanos(0))
• ResourceQuota.builder() static factory returns a new Builder instance

Acceptance Criteria

• All three getters verified for both present and empty states
• Zero-value boundary tests pass without IllegalArgumentException
• mvn clean verify passes