Port gRPC retry and hedging execution

Bun corpus source

• js/third_party/grpc-js/test-retry.test.ts
• sequential corpus position: 3990

Scope

• execute configured unary retry and hedging attempts
• propagate grpc-previous-rpc-attempts metadata without mutating caller metadata
• honor retryable/non-fatal status sets, fatal statuses, backoff, and configured attempt caps
• honor grpc.enable_retries and grpc-node.retry_max_attempts_limit
• preserve terminal causes with target/attempt/mode operation-stack context
• add focused and permanent regression coverage

Tracking: #66

Implemented and published in f18d40cd6 (feat(third-party): port gRPC retry execution).

What landed:

• executable unary retry and hedging attempt orchestration
• isolated per-attempt metadata with grpc-previous-rpc-attempts propagation
• retryable/non-fatal status matching for the complete gRPC status-code set
• fatal-status termination, exponential capped backoff, and hedging delay scheduling
• default five-attempt cap plus grpc-node.retry_max_attempts_limit override
• grpc.enable_retries handling and method/service policy selection
• normalized terminal failures with status/details, target, zero-based attempt, attempt budget, mode, preserved cause, and RetryCall.attempt operation/source stack frames
• permanent end-to-end coverage proving caller metadata remains unmodified

Verification:

• exact Bun file: 15 passed, 0 failed, 0 todo, 0 unsupported
• affected gRPC positions 3985–3990: 113 passed, 4 upstream todos, 0 failed, 0 unsupported
• permanent gRPC diagnostics: 17 passed
• permanent SQL adapter and third-party mini-suite gates: passed
• zig fmt --check packages/home_test/src/corpus_runner.zig: passed
• git diff --check: passed

Sequential corpus ledger through position 3990: 332 executable files, 2,806 passed, 213 upstream todos, 0 failed, 0 unsupported, 171 intentionally allowed-empty files.

Tracking: #66