nisse-review marks a reply that settles its thread; the PR's author resolves it

The reviewer is read-only (R3), so Gitea refuses it resolving a thread.
Now each reply says whether it settles its thread, and a settled reply
carries <!-- nisse-review: settled -->. nisse-dev, as the author, resolves
every comment on that thread's line when it watches the PR, and doesn't
take the settled reply as a point to answer. scripts/resolve_settled.py
does the same for PRs made by hand.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

nisse-dev/tests/test_loop_milestones.py

@@ -78,6 +78,8 @@ class Forge:
         self.approved: dict[int, list[Approval]] = {}
         self.status: dict[str, str] = {}  # commit -> combined check state
         self.agent_merged: list[int] = []
+        self.resolved: list[int] = []  # line comments the agent resolved
+        self.refuse_resolve = False
 
     # intake
     def assigned_issues(self, repo: str, assignee: str) -> list[Issue]:
@@ -171,6 +173,11 @@ class Forge:
     def post_comment(self, repo: str, index: int, body: str) -> None:
         self.posted.append((index, body))
 
+    def resolve_comment(self, repo: str, comment_id: int) -> None:
+        if self.refuse_resolve:
+            raise GiteaError("gitea POST resolve returned 403")
+        self.resolved.append(comment_id)
+
     def post_review(self, repo: str, index: int, *, body, commit, comments=()) -> int:
         if self.refuse_inline:
             raise GiteaError("gitea POST reviews returned 422: line not in diff")