Codifies the limits set in agent/config.yml 2026-10-19: task concurrency 2,
no nested subagent spawns (maxRecursionDepth 1 - and why 0 must never be
set), 30-min runtime / 120-request budgets, isolation opt-in enabled,
completion probes off, 600s tool timeout ceiling, and per-provider
in-flight caps (archon 3, dragoon 2, zealot 3) keyed by models.yml provider
ids with their per-machine scope caveat. Small docs-only change; no issue
opened per trunk-based small-fix exemption.