M3.3: the trust dial (the agent merges approved PRs)

A project's trust.merge is operator (the default) or approved (L3, D5,
#65). Set to approved, the harness, never the model, merges a PR in the
PR watch once an approving review from a gitea.operators account is on
its current commit, its checks pass (none at all counts; pending
waits) and it's mergeable; the item then goes on as after any merge.
Each reason to hold off (failed checks, conflicts, a refused merge) is
said once per commit.

Gitea enforces it: protection requires approvals from an operators-only
whitelist and dismisses stale ones. At start, for each approved
project, the agent checks by behaviour that its own unapproved merge is
refused, with a throwaway branch and PR made through the API (never the
workspace); if it isn't refused, the operator merges until a restart.

- gitea: approvals, combined check status, a PR's head commit and
  mergeability, API-made branches and their deletion.
- Test and bring-up repositories get the protection.
- Tests: the decision (unit), the hard wall on a real Gitea
  (test_trust_live), an e2e test where the operator only approves, and
  a walk property, merges_only_approved, checked against a mutant that
  ignores which commit was approved.

Closes #65

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

@@ -248,3 +248,74 @@ def test_assigned_at_is_the_last_assignment_across_pages() -> None:
 
     assert client(handler).assigned_at("o/r", 6, "dev-agent") == "t4"
     assert client(handler).assigned_at("o/r", 6, "nobody") is None
+
+
+def test_approvals_are_the_standing_approving_reviews() -> None:
+    reviews = [
+        {"state": "APPROVED", "user": {"login": "don"}, "commit_id": "abc"},
+        {
+            "state": "APPROVED",
+            "user": {"login": "don"},
+            "commit_id": "old",
+            "stale": True,
+        },
+        {
+            "state": "APPROVED",
+            "user": {"login": "x"},
+            "commit_id": "abc",
+            "dismissed": True,
+        },
+        {"state": "REQUEST_CHANGES", "user": {"login": "don"}, "commit_id": "abc"},
+        {"state": "COMMENT", "user": {"login": "don"}, "commit_id": "abc"},
+    ]
+    handler = lambda request: httpx.Response(200, json=reviews)
+    approvals = client(handler).approvals("o/r", 3)
+    assert [(a.author, a.commit, a.stale) for a in approvals] == [
+        ("don", "abc", False),
+        ("don", "old", True),
+    ]
+
+
+def test_checks_are_the_combined_status_or_none() -> None:
+    def handler(request: httpx.Request) -> httpx.Response:
+        assert request.url.path == "/api/v1/repos/o/r/commits/abc/status"
+        return httpx.Response(200, json=answer)
+
+    answer: dict = {"state": "", "total_count": 0, "statuses": []}
+    assert client(handler).checks("o/r", "abc") == "none"
+    answer = {"state": "pending", "total_count": 1, "statuses": [{}]}
+    assert client(handler).checks("o/r", "abc") == "pending"
+    answer = {"state": "success", "total_count": 2, "statuses": [{}, {}]}
+    assert client(handler).checks("o/r", "abc") == "success"
+
+
+def test_a_pull_request_carries_its_head_commit_and_mergeability() -> None:
+    data = {
+        **pr_json(5, "m-1"),
+        "head": {"ref": "m-1", "sha": "f00"},
+        "mergeable": True,
+    }
+    pr = client(lambda request: httpx.Response(200, json=data)).pull_request("o/r", 5)
+    assert (pr.head_sha, pr.mergeable) == ("f00", True)
+
+
+def test_a_check_branch_is_made_through_the_api() -> None:
+    seen: list = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen.append((request.method, request.url.path, request.content))
+        return httpx.Response(201, json={})
+
+    gitea = client(handler)
+    gitea.branch_with_file(
+        "o/r", base="main", branch="chk", path="f", text="x", message="m"
+    )
+    gitea.delete_branch("o/r", "chk")
+    body = json.loads(seen[0][2])
+    assert (seen[0][0], seen[0][1]) == ("POST", "/api/v1/repos/o/r/contents/f")
+    assert (body["branch"], body["new_branch"], body["content"]) == (
+        "main",
+        "chk",
+        "eA==",
+    )
+    assert seen[1][:2] == ("DELETE", "/api/v1/repos/o/r/branches/chk")