session-handoff v0.7.4-jev (parallel prerelease)

This is a parallel prerelease alongside 0.7.4, not its successor: same base as 0.7.4, plus an opt-in TypeSafe/Jev integration. Everything below is off by default and requires an explicit choice plus your own TypeSafe credentials; a plain 0.7.4 install is unaffected.

• Add an opt-in TypeSafe/Jev backend for the checkpoint tool-summary scorer (SESSION_HANDOFF_CHECKPOINT_SCORER=typesafe), alongside the existing local-Ollama option — unset behaves exactly as plain 0.7.4.
• Add server/typesafe_client.py: a fail-open TypeSafe (Jev) client with bidirectional secret redaction, used by both the checkpoint scorer and the benchmark judge below.
• Add a TypeSafe/Jev benchmark judge (benchmark/typesafe_judge.py) that can batch-fill judge.json for every blind run under a study, without weakening the existing release gate (18+ calibration samples, 80%+ agreement, human-reviewed) documented in benchmark/JUDGE.md.
• Add an opt-in compact-advisor Stop hook (SESSION_HANDOFF_COMPACT_HINT=typesafe) that suggests, never forces, running /compact at a good checkpoint. Score and floor math ported and attributed from kunchenguid/compact-adviser (MIT), whose eval harness validated these thresholds against real session checkpoints.
• doctor reports TypeSafe configuration status (configured: bool only, no network call, keeping its provider_calls: 0 contract).

Full changelog: docs/CHANGELOG-0.7.4-jev.md