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.

tools/save.md

@@ -0,0 +1,26 @@
+---
+description: Save the current Claude Code session into MemPalace. Idempotent — won't dupe.
+---
+
+# /save
+
+Save the current Claude Code session into MemPalace. Run this when you
+want a checkpoint. Safe to run repeatedly — drawer IDs are content-hashed
+so re-running on the same session overwrites in place, no duplicates.
+
+Behavior:
+
+1. Find the current session's JSONL transcript path (Claude Code passes
+   it via the conversation context — look for `~/.claude/projects/` paths).
+2. Run via bash:
+
+   ```
+   mempalace mine "<TRANSCRIPT_PATH>" --mode convos --wing claude_imports
+   ```
+
+3. If the user supplied an argument after `/save`, use it as the wing name
+   instead of `claude_imports` (e.g. `/save my_research` →
+   `--wing my_research`).
+4. Report back: how many drawers were filed, into which wing/room.
+
+Requires `mempalace` to be installed (`pip install mempalace`).