Testing: Scenarios that run today (T-02) #336

Part of the test strategy (captain, 2026-10-05: scenarios that test the changes together; cleaner, faster suites; TESTING.md). Epic #305.

Scope. S1 agent lifecycle, S7 concurrent claim, S9 retraction through recursion and negation, S12 restart mid-scenario, S15 multi-tenant and scoped keys, exactly as tabled in report Section 7.4, on the shop pack, asserting rows, deltas, revisions, structured errors and others_unaffected.

Acceptance. Five scenarios green on main against recompute; each names in its doc comment the captain's table row and the milestone 9 issues it gates; S9's history is also fed to the differential oracle (scenarios::oracle_check) and agrees; total added run time under 30 s.