aad56e5bf9
Update plan header :
- v2 (Task 18) + v3 (Task 19) extensions chronology
- Studio train validated, ckpt action_head_v3.pt landed
- Mesh NaN-guard debug trail (commit 4e7101c)
- Branch convergence main == feat/action-head
- Pointers to memories project_action_head_v3, etc.