fix(issue-18): default ack timeout T = 180 s

In the v4.5.0 review round grok read the brief and published `started`
70 s after the injection; with T = 60 the wrapper had already closed the
job as agent_blocked and refused its later PASS. T bounds delivery, not
work, so a generous default costs nothing when the agent answers fast.
Code, docs and the CLI snapshot updated together.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/multi-agent-mux-delegate-job/SKILL.md

@@ -40,7 +40,7 @@ multi-agent-mux-delegate-job submit \
   --agent-session herdr:<session_name> \
   --prompt "Task description or instructions here" \
   --role <Worker|Planner|Reviewer> \
-  --timeout 3600 [--heartbeat 30 --heartbeat-misses 4 --ack-timeout 60] [--idle-timeout <sec>]
+  --timeout 3600 [--heartbeat 30 --heartbeat-misses 4 --ack-timeout 180] [--idle-timeout <sec>]
   #   Liveness contract (Issue #18): the agent heartbeats every N s (automatic),
   #   the job is unresponsive after K x N s (--idle-timeout overrides), `started`
   #   must arrive within T s of the injection or the inject fails closed.