Replace the hardcoded 20-call turn budget with user settings: a global
model-call limit that every turn inherits (headless/knowledge work,
scheduled agents, sub-agents) plus an optional chat-only override for
interactive turns. Settings live in config/turn_limits.json (1-100,
default 20) and are edited from a new Advanced tab in Settings.
The limit is resolved at turn creation via an ITurnLimitsResolver
injected into TurnRuntime, keyed on humanAvailable; explicit per-call
overrides still win, and the resolved value is persisted in
turn_created.config.maxModelCalls as before, so historical and
in-flight turns are unaffected by settings changes. Sub-agents now
default to and are capped by the global limit instead of the constant.
eece1af90e