test: report native job restart substages

[roodboi]

The completed-job worktree test reports only alpha-restart-4 when any of several restart checks fails. Add closed substages around the original seed inspection, CLI result, fresh completion, pending receipt, SQL readiness/counts, and sibling isolation so the next failure identifies the boundary that failed.

Diagnostics preserve callback results, original errors, assertions, order, deadlines and cleanup. They emit only fixed fields and allowlisted CLI-code buckets; raw replies, values, paths, IDs and arbitrary errors are omitted. This does not claim to explain or fix the earlier hosted restart failure.

Validation: independent review against current next, five focused controls / 39 assertions, changed-file lint, CLI typecheck, privacy and diff checks passed. The initial local typecheck lacked the tracked YAML dependency; bun install --frozen-lockfile restored it and typecheck passed. All three diagnostic blobs are carried unchanged from the separately reviewed build branch. Fresh exact-head CI remains required.

Release intent: test-only diagnostics; production and release behavior are unchanged.

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