A repository per test run instead of the shared sandbox

Every live test that touches a repository gets one of its own from
e2e_support.fresh_repo, made by the test operator as an operator makes a
project's (D4, D8): seeded from tests/integration/seed/ (the sandbox's
package, without past runs' leftovers), the agent's account a collaborator
with write access, main protected (pushes only by the owner, an approval to
merge), and a deploy key generated for the run. It is deleted afterwards
(NISSE_E2E_KEEP_REPOS keeps it); scripts/e2e-cleanup.sh deletes leftovers.

- Both e2e fixtures use it; per-run base branches are gone. The merge
  helper approves first, as the protection now requires.
- test_gitea_live uses it, so CI needs NISSE_OPERATOR_TOKEN and no longer
  writes the sandbox deploy key (NISSE_PUSH_KEY).
- A live test of the helper: seeded, shared with the agent, protected
  against it, deleted.
- nisse-test.yaml's project entry is a placeholder; pytest and ruff skip
  the seed.

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

tests/integration/test_gitea_live.py

@@ -1,19 +1,18 @@
-"""Live Gitea round trip against the sandbox repo: push a branch, open a PR,
-comment, and prove the L8 reconciler reads external truth correctly.
-
-Cleans up after itself (closes the PR, deletes the branch) so repeated runs
-do not silt up the sandbox.
+"""Live Gitea round trip in a repository of the run's own: push a branch,
+open a PR, comment, and prove the L8 reconciler reads external truth
+correctly, and that protection holds against the agent (D4).
 """
 
 import uuid
 from pathlib import Path
 
 import pytest
+from e2e_support import fresh_repo, operator_gitea
 
-from nisse_dev.agent import push_credential, remote_url
+from nisse_dev.agent import remote_url
 from nisse_dev.config import AgentConfig
 from nisse_dev.execution import SSHHost
-from nisse_dev.git import GitError, GitRepo
+from nisse_dev.git import GitError, GitRepo, SSHKey
 from nisse_dev.gitea import GiteaClient, pull_request_reconciler
 from nisse_dev.state import Intent
 
@@ -34,9 +33,21 @@ def intent_for(branch: str) -> Intent:
 def test_push_open_pr_and_reconcile(
     tmp_path: Path, live_config: AgentConfig, gitea: GiteaClient, ssh_host: SSHHost
 ) -> None:
-    repo_path = live_config.gitea_repo  # the sandbox
     client = gitea
+    with fresh_repo(
+        operator_gitea(live_config.gitea_url),
+        uuid.uuid4().hex[:8],
+        tmp_path / "keys",
+        agent=client.whoami(),
+    ) as fresh:
+        _round_trip(
+            tmp_path, client, ssh_host, fresh.name, SSHKey(fresh.push_key.read_text())
+        )
 
+
+def _round_trip(
+    tmp_path: Path, client: GiteaClient, ssh_host: SSHHost, repo_path: str, key: SSHKey
+) -> None:
     account = client.whoami()
     assert "testing" in account, (
         f"live tests must run as a testing account, not {account}"
@@ -49,12 +60,12 @@ def test_push_open_pr_and_reconcile(
     assert reconcile(intent_for(branch)) is False
 
     # Pushed the way the agent does: from the build VM (here the throwaway
-    # sshd), with the push credential the config names, never the API token.
-    key = push_credential(live_config)
-    assert key is not None, "nisse-test.yaml names no push credential (D4)"
+    # sshd), with the repository's deploy key, never the API token.
     url = remote_url(client, repo_path, key)
     repo = GitRepo(ssh_host, tmp_path / "work", known_hosts=str(tmp_path / "kh"))
     repo.init()
+    repo._git("fetch", "-q", url, "main", credential=key)
+    repo._git("checkout", "-q", "-B", "work", "FETCH_HEAD")
     repo.configure_identity(account, f"{account}@example.test")
     (repo.root / f"{branch}.txt").write_text("live test artifact\n")
     assert repo.commit_all("Live test commit") is not None
@@ -93,5 +104,4 @@ def test_push_open_pr_and_reconcile(
     finally:
         if pr is not None:
             client.close_pull_request(repo_path, pr.number)
-        repo.delete_remote_branch(url, branch, credential=key)
         client.close()