Add the abandon command

A4 already names abandon as one of the ways out of a halt (continue,
re-plan, or abandon) and 0.2 closes a work item as completed or
abandoned, but no command did it: from a gate or a question the only way
to drop a task was to edit the state database.

- 'abandon' ends the task from any waiting state and returns to IDLE.
  The move is made durable first; then the plan issue and any open
  milestone PR are closed with a note (branches kept), and any
  unresolved intent is aborted so boot reconciliation does not gate on
  work dropped on purpose. A Gitea failure is reported, not fatal.
- Like 'status' it is a command in every state, never read as an answer
  or feedback. While work runs, 'stop' comes first, as before.
- The restart / stranded question and the PR_OPEN hints mention it.
- Spec: B1 gains the abandon edge and B2 the command.

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

nisse-dev/tests/test_gitea.py

@@ -1,4 +1,5 @@
 import json
+from pathlib import Path
 
 import httpx
 import pytest
@@ -195,3 +196,40 @@ def test_intent_without_a_branch_is_unverifiable() -> None:
         resolved_at=None,
     )
     assert pull_request_reconciler(client(handler), "o/r")(blank) is None
+
+
+def test_closing_comments_first_then_closes_issue_and_pr() -> None:
+    from nisse_dev.approvals import PlanBoard
+    from nisse_dev.git import GitRepo
+    from nisse_dev.publish import MilestonePublisher
+
+    seen: list[tuple[str, str, dict]] = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        body = json.loads(request.content) if request.content else {}
+        seen.append((request.method, request.url.path, body))
+        if request.method == "POST":
+            return httpx.Response(
+                201, json={"id": 5, "user": {"login": "bot"}, "body": body["body"]}
+            )
+        return httpx.Response(201, json={})
+
+    gitea = client(handler)
+    PlanBoard(gitea, "o/r").close(10, "abandoned by don")
+    publisher = MilestonePublisher(
+        None,  # type: ignore[arg-type] -- closing touches neither store nor git
+        gitea,
+        "o/r",
+        GitRepo(Path(".")),
+        base_url="https://gitea.test",
+        account="bot",
+        token="tok",
+    )
+    publisher.close_pull_request(20, "abandoned by don")
+
+    assert seen == [
+        ("POST", "/api/v1/repos/o/r/issues/10/comments", {"body": "abandoned by don"}),
+        ("PATCH", "/api/v1/repos/o/r/issues/10", {"state": "closed"}),
+        ("POST", "/api/v1/repos/o/r/issues/20/comments", {"body": "abandoned by don"}),
+        ("PATCH", "/api/v1/repos/o/r/pulls/20", {"state": "closed"}),
+    ]