The new loop's core: intake, restatement, go-ahead, threads (M2.1, PR B)

nisse_dev.loop runs alongside control.py, chosen with `loop: new`.
Issues assigned to the agent (by an operator, or filed by one) become work
items, each with a Matrix thread. A driver run is one model with tools
until it calls a waiting tool: restate puts rev-N up for a go-ahead, bound
to the revision on screen when the reply arrived; ask_human waits for an
answer; close_item closes the item and its issue. Before the go-ahead the
driver can look but not change or close anything. One item is active at a
time; replies in an item's thread go to it. On boot, an item cut off
mid-run waits on the operator, and waiting points are put up again.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/src/nisse_dev/main.py

@@ -27,7 +27,12 @@ def main() -> int:
         print(f"nisse-dev: {exc}", file=sys.stderr)
         return 2
 
-    agent = build_agent(config)
+    if config.loop == "new":
+        from nisse_dev.loop.build import build_loop_agent
+
+        agent = build_loop_agent(config)
+    else:
+        agent = build_agent(config)
 
     def shutdown(_signum: int, _frame: FrameType | None) -> None:
         print("nisse-dev: stopping", file=sys.stderr)