Automate the per-project retrofit (git audit, verify, scope, commit,
validate) as a main-thread slash command that asks for the judgment
calls. Step 1 (mining a past chat) stays manual — the command surfaces
which conversation to mine and hands back, since it can't resume one.
Document the portability protocol (vendor-neutral knowledge, vendor-named
symlinks) and a Claude subagents reference handbook, and link the
portability protocol from the retrofit playbook.