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/config.py

@@ -59,6 +59,7 @@ OPTIONAL_KEYS = (
     "gitea.push_token",
     "build_host.user",
     "build_host.port",
+    "loop",
 )
 
 _REFERENCE = re.compile(r"\$\{([A-Za-z_][A-Za-z0-9_]*)\}")
@@ -254,6 +255,9 @@ class AgentConfig:
     max_output_tokens: int = DEFAULT_MAX_OUTPUT_TOKENS
     request_timeout_s: float = DEFAULT_REQUEST_TIMEOUT_S
     tuning: Tuning = field(default_factory=Tuning)
+    # Which loop runs: "old" (control.py) until the switch-over (M2.8), or
+    # "new" (nisse_dev.loop).
+    loop: str = "old"
     config_file: Path | None = None
 
     @classmethod
@@ -338,6 +342,9 @@ class AgentConfig:
                 raise ValueError
         except (TypeError, ValueError):
             errors.append("build_host.port: must be a TCP port number")
+        loop = str(values.get("loop") or "old")
+        if loop not in ("old", "new"):
+            errors.append("loop: must be old or new")
         push_user = values.get("gitea.push_user")
         push_token = values.get("gitea.push_token")
         if bool(push_user) != bool(push_token):
@@ -384,6 +391,7 @@ class AgentConfig:
             max_output_tokens=max_output,
             request_timeout_s=request_timeout,
             tuning=tuning,
+            loop=loop,
             config_file=config_file,
         )
         config._refuse_secrets_inside_the_clone(env)