feat(sdk): add DECO_OTEL_ACCESS_LOG_RATE sampling for INFO access logs

[igoramf]

Summary

• Adds DECO_OTEL_ACCESS_LOG_RATE env var (float 0–1, default 1.0 = 100% = current behavior) to control INFO access log volume
• 5xx requests always emit an ERROR-level access log regardless of the rate — errors are never sampled
• Sampling uses FNV-1a 32-bit hash of requestId/traceId for consistent per-request decisions (same request always gets the same pass/drop outcome)
• Falls back to Math.random() only when no request ID is available

Why

logRequest() emits 1 INFO log per HTTP request. casaevideo + bagaggio alone generate ~2,200 INFO access logs/minute at otel-ingest, even though 99% are discarded after arrival. Moving the sampling decision to the SDK (before the POST) reduces otel-ingest load and billing.

Recommended prod config:

DECO_OTEL_ACCESS_LOG_RATE=0.1   # sample 10% of INFO access logs; 5xx always logged

Test plan

• Default (DECO_OTEL_ACCESS_LOG_RATE unset): 100% of access logs emitted — same as before
• DECO_OTEL_ACCESS_LOG_RATE=0: 0 INFO access logs; 5xx still emit ERROR log
• DECO_OTEL_ACCESS_LOG_RATE=0.1: ~10% of INFO access logs pass; 5xx always pass
• FNV-1a consistency: same requestId always gets same pass/drop decision

🤖 Generated with Claude Code

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Summary by cubic

Adds DECO_OTEL_ACCESS_LOG_RATE to sample INFO access logs and reduce otel-ingest volume. Default remains 100% (no behavior change).

• New Features

  • Sample INFO access logs via DECO_OTEL_ACCESS_LOG_RATE (0–1; default 1.0).
  • 5xx requests always log at ERROR level (never sampled).
  • Deterministic per-request sampling using FNV-1a hash of requestId/traceId; falls back to Math.random() if missing.

• Migration

  • Set DECO_OTEL_ACCESS_LOG_RATE=0.1 in production to keep ~10% of INFO logs.

^{Written for commit 2bcc74b. Summary will update on new commits.}