The queue: parking, the operator's order, blocked items (M2.2)

Several work items on the new loop (L1, D4):
- Switching parks the item on the workspace: its work is committed and its
  branch pushed; resuming checks the item's branch back out. Branches of
  open items are never set aside by a fresh workspace.
- Next item: the operator's "do #N next" first, otherwise the oldest.
- Issues with open Gitea dependencies are blocked until they close, checked
  at intake and on every round; status shows blocked items and the line.

Tests: queue unit tests, the property walk over several issues with
dependencies and a new parked_work_safe property (it catches parking
disabled), and an end-to-end test with two issues where B depends on A.

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/gitea.py

@@ -237,6 +237,16 @@ class GiteaClient:
             if not item.get("pull_request")
         ]
 
+    def open_dependencies(self, repo: str, index: int) -> list[str]:
+        """The issues this one depends on that are still open, as
+        "owner/repo#N": what blocks it (L1)."""
+        data = self._request("GET", f"/repos/{repo}/issues/{index}/dependencies")
+        return [
+            f"{(item.get('repository') or {}).get('full_name', repo)}#{item['number']}"
+            for item in data or []
+            if item.get("state") == "open"
+        ]
+
     def assigned_by(self, repo: str, index: int, assignee: str) -> str | None:
         """Who last assigned the issue to ``assignee``, from its timeline;
         None if the timeline doesn't say."""