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/tests/test_loop.py

@@ -48,6 +48,10 @@ class FakeGitea:
         self.assigner = assigner
         self.comments: list[tuple[int, str]] = []
         self.closed: list[int] = []
+        self.deps: dict[int, list[int]] = {}
+
+    def open_dependencies(self, repo: str, index: int) -> list[str]:
+        return [f"{repo}#{n}" for n in self.deps.get(index, []) if n not in self.closed]
 
     def assigned_issues(self, repo: str, assignee: str) -> list[Issue]:
         return [i for i in self.issues if i.number not in self.closed]