perf(erpc:PLA-691): burst coalescing and deterministic negative cache

[0x666c6f]

Summary

• Reduce duplicate upstream reads during burst traffic.
• Add deterministic short-lived negative caching for safe read-error classes.

Changes

• add post-completion burst coalescing window (40ms) for eligible read methods
• gate coalescing on method/finality/pending/nonce-sensitive rules
• add deterministic negative cache (200ms TTL) keyed by method+finality+request hash
• store only non-retryable deterministic errors; bypass pending/nonce-sensitive/stateful/directive paths
• add metrics:
  • erpc_network_burst_coalesced_request_total
  • erpc_network_deterministic_negative_cache_set_total
  • erpc_network_deterministic_negative_cache_hit_total
• add tests for burst coalescing and negative-cache behavior
• update monitoring docs with new metrics and PromQL examples

Linear

• PLA-691: https://linear.app/morpho-labs/issue/PLA-691/erpc-burst-coalescing-deterministic-negative-cache-for-read-methods

[chatgpt-codex-connector]

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