Add critical log soak QA gate

Docs/QA/MvpQaGates.md

@@ -229,3 +229,25 @@ Required evidence:
 
 This gate is server-relevant and must be rechecked after the final 0.1.Q server
 package/deploy if server code or package contents changed.
+
+## Thirty-Minute Critical Log Soak
+
+The 30-minute critical log soak gate proves the MVP can run through a short
+investor/tester session without noisy fatal, crash, assertion, ensure, or
+critical error spam hiding real problems.
+
+Required evidence:
+
+- Run a packaged client and the target server for at least 30 minutes.
+- Exercise the normal MVP loop during the soak: join, gather, craft/use fire,
+  craft/place shelter, wait through time/weather pressure, disconnect, and
+  reconnect if possible.
+- Preserve client logs, server logs, and any visual QA summary under `Saved`
+  or the release evidence folder.
+- Run `Scripts/scan_critical_log_spam.py` against those logs.
+- A passing scan reports zero fatal/crash/assert/ensure/critical-error matches.
+- Any known noisy-but-harmless line must be added to the scanner allowlist with
+  a short comment in the commit that introduced the allowlist entry.
+
+This gate is both client and server relevant. It must be re-run for final
+milestone packages before sending an investor demo as stable.