📝 Add Solidity Incident Resolution

Signed-off-by: pcaversaccio <pascal.caversaccio@hotmail.ch>

Author: pcaversaccio

ACTIVITY.md

@@ -2,6 +2,7 @@
 
 This is a continually evolving, albeit incomplete, public record of incidents in which SEAL 911 has played a pivotal role in their resolution.
 
+- [Solidity `TSTORE` poison bug incident resolution](https://www.soliditylang.org/blog/2026/02/18/transient-storage-clearing-helper-collision-bug)
 - [CometBFT consensus-level vulnerability patch](https://github.com/cometbft/cometbft/security/advisories/GHSA-c32p-wcqj-j677)
 - [Makina incident resolution](https://makinafi.substack.com/p/post-mortem-january-20th-2026-incident)
 - [IPOR incident resolution](https://x.com/ipor_io/status/2008728627190321480)