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>

tests/acp.test.ts

@@ -233,7 +233,7 @@ test("the terminal: a real shell through the link, only where remote.terminal sa
   config(fake.url)
   const root = project()
   const off = await client({ roots: [root], maxMode: "edit", approvalTimeoutMs: 50, requireTrust: true })
-  expect(off.init._meta.lembas.capabilities).toEqual(["directories", "configure", "steer", "sessions", "status", "delete", "compact", "title", "files", "commands", "attachments", "ask", "plan", "model", "turns", "context", "library", "prototypes", "plan_state", "rewind"])
+  expect(off.init._meta.lembas.capabilities).toEqual(["directories", "configure", "steer", "sessions", "status", "delete", "compact", "title", "files", "commands", "attachments", "ask", "plan", "model", "turns", "context", "library", "prototypes", "plan_state", "rewind", "jobs"])
   await expect(off.c.request("_lembas/terminal/open", { cwd: root })).rejects.toThrow("remote.terminal is off")
 
   const { c, init } = await client({ roots: [root], maxMode: "edit", approvalTimeoutMs: 50, requireTrust: true, terminal: true })