Wait a grace period before switching away from a waiting item

Switching as soon as the active item posts a plan or question means the
operator sees the request and the switch notice seconds apart. A prompt
approval then waits until the other item waits or closes, which can be
a whole milestone. A configurable grace period (default 10 minutes)
lets a watching operator answer before the agent moves on, and still
switches when they are away.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/Architecture-Build-Spec.md

@@ -170,6 +170,13 @@ come back to something. Components throughout this document refer to them.
 
   Either way, it posts a notice naming both items and why it chose that one. The
   agent never switches away from an item that is working.
+- **A grace period comes before switching away from a waiting item.** After the
+  active item posts a plan or a question, the agent waits a configurable period
+  (default 10 minutes) before switching. An operator who is watching answers in
+  that time and the item carries on without a switch. Otherwise their approval
+  could sit behind a long milestone on the other item: once parked, an item only
+  becomes active again when the active one waits or closes. Closing an item needs
+  no grace period.
 - **A parked item is ready when the agent can act on it without the operator:** it
   has not started yet (a duty finding, a ticket), or intake arrived while it was
   parked that answers what it was waiting for (an approval, an answer, a review