Harness spec 2.0.0: background work is a job — commands and subagents alike, seen and steered

One registry per process, every job owned by a session: bash's background commands (and a command
still running at its timeout, which now goes to the background instead of being killed) and
subagents started with task background: true. job_list, job_output, job_stop (the former
bash_list, bash_output, bash_kill) and the new job_send and report; a finished job wakes the owning
session in every front end with its marked note. The TUI counts jobs, lists them (/jobs), opens a
command's output, enters a subagent and messages it, moves a command to the background (ctrl+b)
and asks before quitting with jobs running. The link gains the jobs capability. Subagents get a
session row of their own, the spec's preamble and agent texts, and their errors reach the report.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

harness/VERSION

@@ -1 +1 @@
-1.2.0
+2.0.0