Harness spec 3.2.0: effort levels, the thinking switch, parallel capacity

models/schema.json: thinking_switch (the server turns thinking off for
chat_template_kwargs.enable_thinking: false) and capacity.parallel
(single_session is parallel 1). The level `off` exists only with the
switch and sends enable_thinking false and no effort; a model that takes
no efforts has the one level `default`, which sends nothing. The levels a
chat offers are (off) + efforts; one level shows no control, [off, X] a
Thinking switch, more a slider. A start level and a level the model does
not offer follow one rule. quirks.json: thinking-default; acp.md: effort
values are levels. New conformance area: levels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

harness/loop.json

@@ -34,7 +34,7 @@
     "about": "Calls in one step run together, at most 4; a call that waits on the user (ask_user, plan_submit) runs alone; two calls on one file run in order. A tool's error is its result, never the end of the prompt.",
     "max": 4
   },
-  "capacity": "A subagent (task) is not started on a model whose server cannot hold it beside the prompt's own model — or beside the model of a subagent already running: another model of a connection that holds one model at a time, or the same model when it serves one request at a time (models/schema.json capacity).",
+  "capacity": "A subagent (task) is not started on a model whose server cannot hold it beside the prompt's own model — or beside the model of a subagent already running: another model of a connection that holds one model at a time, or the same model when it already serves as many of this session's requests as it can at once (models/schema.json capacity: `parallel`, `single_session` being parallel 1). A team's members are not refused there: they wait for a slot (team.md, Capacity).",
   "jobs": {
     "about": "Background work owned by a session: a command (bash `background: true`, or one still running when its timeout passed) or a subagent (task `background: true`). One id sequence per session (job1, job2, …), one list (job_list), one way to read (job_output), to stop (job_stop) and, for a subagent, to message (job_send); a subagent's own tools see only the jobs it started. A job that ends wakes the session that owns it: while a prompt runs, as a user message at the next step boundary; otherwise as a new turn of its own, marked `machine` so a UI shows it as the harness's, not the person's. A session that is not open keeps the note until it is resumed. Every such message begins with its mark, said rather than hidden: a model refuses an unmarked one as an injection (conformance/jobs.json gives the texts).",
     "marks": {