perf(decrypt): silence per-attempt warn logs that saturate stdout

PRODUCTION BUG (still present after PR #396, #402): inbound 60s latency.
Diff vs Pedro snapshot pinpointed the residual cause: pino warn-level
logs of `errorContext` (key + jid + err + sender + author + decryptionJid
+ flags) on EVERY decrypt failure attempt.

Under WA's LID/DSM rollout the user's own DSM floods the inbound pipeline
with Bad MAC / "Key used already" / "No session record" errors when the
auth state has a legacy `_1.0` session that no longer matches the
LID-addressed envelope. At ~30 failed attempts/min this is ~30 JSON lines/sec
of full key+context dumps. pm2 writes stdout synchronously; once the pipe
buffer fills, `process.stdout.write` BLOCKS the event loop. Inbound
delivery, query responses, profile-pic loads — everything stalls.

Pedro doesn't have this rich logging; libsignal's own console.error is
already intercepted in src/index.ts and reformatted as a single emoji line
("🔐 Bad MAC Error | JID: 1940****_1.0"). The duplicated pino warn was
pure noise.

THIS PATCH:
- Per-attempt warn → debug. With BAILEYS_LOG_LEVEL=warn (production) these
  drop entirely. With LEVEL=debug they still surface for active
  troubleshooting.
- Retry-exhausted warn (rare) keeps a SLIM context: msgId + jid + slimErr
  + attempts. No more full key/sender/author/decryptionJid dump.
- error → warn for retry-exhausted (level 50 is reserved for unknown
  errors that fall through to the else branch — those are real bugs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Utils/decode-wa-message.ts

@@ -454,19 +454,40 @@ export const decryptMessageNode = (
 							...(isRetryExhausted && { retriesExhausted: true, attempts: err.attempts })
 						}
 
-						// Smart logging based on error type and retry status
+						// Smart logging based on error type and retry status.
+						//
+						// PERF NOTE: under WhatsApp's LID/DSM rollout, own DSM messages flood
+						// the inbound pipeline with Bad MAC / "Key used already" / "No session
+						// record" errors *every* time the auth state has a session in the
+						// legacy `_1.0` format that no longer matches the LID-addressed
+						// envelope. Logging the full errorContext (key + jid + err) per failed
+						// attempt as warn-level produces tens of JSON lines/sec, which
+						// saturates stdout in pm2 (synchronous writes to a full pipe block the
+						// event loop). The clean `🔐 Bad MAC Error | JID: …` line emitted by
+						// the console.error interceptor in src/index.ts already gives an
+						// operator-visible signal — the duplicated pino line was pure noise.
+						//
+						// We now only emit warn-level when retries are exhausted (rare,
+						// actionable). Per-attempt detail is still available at debug level
+						// (BAILEYS_LOG_LEVEL=debug) for active troubleshooting.
+						const slimErrorContext = {
+							msgId: fullMessage.key?.id,
+							jid: fullMessage.key?.remoteJid,
+							err: slimErr,
+							attempts: isRetryExhausted ? err.attempts : 1
+						}
+
 						if (isCorrupted) {
-							// Corrupted session errors are expected and auto-recovered
-							// Only log as ERROR if retries exhausted, otherwise WARN on first attempt
+							// Corrupted session errors are expected — Signal Protocol auto-recovers
+							// via retry receipt → pkmsg → new session.
 							// eslint-disable-next-line max-depth
 							if (isRetryExhausted) {
-								logger.error(
-									errorContext,
+								logger.warn(
+									slimErrorContext,
 									`⚠️ Session corrupted after ${err.attempts} attempts. Retry+pkmsg flow will recover.`
 								)
 							} else {
-								// First occurrence - log as warning since auto-recovery will attempt
-								logger.warn(errorContext, '⚠️ Corrupted session detected - attempting auto-recovery')
+								logger.debug(errorContext, '⚠️ Corrupted session detected - attempting auto-recovery')
 							}
 
 							// Session cleanup is deferred to retry exhaustion (safety net).
@@ -479,7 +500,7 @@ export const decryptMessageNode = (
 							// Session record errors are transient - retry should handle them
 							// eslint-disable-next-line max-depth
 							if (isRetryExhausted) {
-								logger.error(errorContext, `Failed to decrypt: No session record found after ${err.attempts} attempts`)
+								logger.warn(slimErrorContext, `Failed to decrypt: No session record found after ${err.attempts} attempts`)
 							} else {
 								logger.debug(errorContext, 'No session record - will retry')
 							}