v2026.5.29-zmb.2 — split-token accessors (session-reset fix)

Supersedes v2026.5.29-zmb.1. Same split-token accessors atop upstream nullclaw/nullclaw v2026.5.29 (commit b25c6eb), now with one correctness fix:

• Session reset clears the split counters. clearSessionState() (the /new and /reset path) zeroes prompt_tokens_total and completion_tokens_total alongside total_tokens, so an embedder metering by-side no longer sees stale per-session figures while tokensUsed() reads 0 after a reset. Caught by greptile on #1.

Suite parity unchanged: pristine v2026.5.29 and this release fail only the same 5 pre-existing redis-environment integration tests. Pin consumers at this tag; zmb.1 is superseded.