docs: add 30-day expiry callout + ship 4 auto-save tools

Adds a brief [!IMPORTANT] callout at the top of the README pointing
users to the urgent announcement at #1388. Claude Code auto-deletes
local JSONL transcripts after 30 days; users without the auto-save
hooks wired are losing transcript data off the rolling window.

Ships 4 small standalone tools at tools/:
- backup_claude_jsonls.sh — rsync ~/.claude/projects/ to a safe folder
- render_jsonl.py — convert JSONL transcripts to readable text
- find_orphan_claude_jsonls.sh — scan backup locations for orphan
  Claude Code transcripts (multi-line shape detection + topic preview)
- save.md — Claude Code slash command for manual /save into MemPalace

Tools verified by independent agent against v3.3.4 source.
Read-only on user data. POSIX bash + Python stdlib only.

README.md

@@ -6,6 +6,10 @@
 > domain — including `mempalace.tech` — is an impostor and may distribute
 > malware. Details and timeline: [docs/HISTORY.md](docs/HISTORY.md).
 
+> [!IMPORTANT]
+> **🚨 Claude Code sessions expire in 30 days w/out auto-save hooks wired!** **[Read this →](https://github.com/MemPalace/mempalace/discussions/1388)**
+
+
 <div align="center">
 
 <img src="assets/mempalace_logo.png" alt="MemPalace" width="240">