pi-durable Kill duel

Same deterministic 5-step hash task on two durable runtimes. Kill one or both mid-step; each must resume from its own log and finish with the same hash.

• Task: part_i = sha256(seed:i), i = 1..5, final = sha256(part_1 … part_5) (joined, no separator).
• Kill left: the Durable Object calls ctx.abort() mid-step. An alarm wakes a fresh instance, which reopens the SQLite storage and runs harness.resume().
• Kill right: a second invocation takes the World session over. The running step's next commit is refused and throws, and the killer exits without resuming. A Vercel Queue wake reopens the session after recoverAfterMs = 5s.
• PASS shows only when both hashes equal the expected hash for this seed.