fix(metrics): expose scheduler and resource budgets

[ketor]

Problem

The native v2.14 client snapshot exports read-scheduler and process-wide RDMA resource metrics, but CLIENT_METRIC_SPECS silently drops them. SGLang/HiCache /metrics therefore cannot show queue delay, pending/active shards, budget saturation, or admission timeouts.

Fix

• allow-list all 5 read-scheduler families
• allow-list all 5 resource-budget families with bounded kind=used|limit labels
• include the adjacent endpoint-cache hit/miss/eviction counters
• add parser, label, counter-delta, gauge-update, and unknown-family regression coverage

Verification

• focused HiCache poller tests: 7 PASS
• native snapshot delta test: PASS
• release contract: 3 PASS
• complete local CTest: 405 PASS, 284 conditional SKIP, 0 FAIL
• exhaustive client snapshot comparison: no remaining non-histogram client metric omissions