docs: add production sync testing guide and log sanitizer script

Add infrastructure for iterative debugging of sync against production data:
- scripts/sanitize-logs.sh: Truncates verbose log lines for LLM analysis
- docs/how-to/production-sync-testing.md: Step-by-step guide for testing
  sync against real relays, identifying issues, and improving logging

1 files changed, 12 insertions, 0 deletions

diff --git a/docs/how-to/README.md b/docs/how-to/README.md
index ed5f014..ba58c08 100644
--- a/docs/how-to/README.md
+++ b/docs/how-to/README.md
@@ -36,6 +36,18 @@ How-to guides are **recipes** that show you how to solve specific problems or ac
 
 ---
 
+### [Test Sync Against Production Data](production-sync-testing.md)
+**Problem:** Debug and improve sync using real-world data  
+**Difficulty:** Intermediate
+
+**You'll learn:**
+- Run sync against production relays
+- Sanitize logs for LLM analysis
+- Identify common issues and patterns
+- Iteratively improve sync behavior
+
+---
+
 ## Planned How-To Guides
 
 ### Deploy ngit-grasp