feat(orchestrator): author allowlist for inbound external-PR review

At ingest, a non-empty external_pr_author_allowlist restricts which external
PRs are reviewed to those GitHub logins (case-insensitive). An empty allowlist
(default) reviews every external PR — safe because the review is read-only; the
confirmed_by_human gate still guards any later supersede that runs fork code.
Unit-tested (_pr_author_allowed).

roboco/runtime/orchestrator.py

@@ -4569,12 +4569,15 @@ Start by:
         task_service = get_task_service(db)
         projects = await get_project_service(db).list_all(active_only=True)
         system_id = _foundation.AGENTS["system"].uuid
+        allowlist = {a.lower() for a in settings.external_pr_author_allowlist}
         ingested = 0
         for project in projects:
             for pr in await git.list_open_prs(project.slug):
                 number = pr.get("number")
                 if number is None or not self._is_external_pr(pr):
                     continue
+                if not self._pr_author_allowed(pr, allowlist):
+                    continue
                 created = await task_service.ingest_external_pr(
                     project_id=cast("UUID", project.id),
                     pr=pr,
@@ -4586,6 +4589,18 @@ Start by:
         await db.commit()
         return ingested
 
+    @staticmethod
+    def _pr_author_allowed(pr: dict[str, Any], allowlist: set[str]) -> bool:
+        """With a non-empty allowlist, only those GitHub authors are reviewed.
+
+        An empty allowlist (the default) reviews every external PR — the review
+        is read-only, so it is safe; the ``confirmed_by_human`` gate still
+        protects any later supersede that would run the contributor's code.
+        """
+        if not allowlist:
+            return True
+        return (pr.get("user_login") or "").lower() in allowlist
+
     @staticmethod
     def _is_external_pr(pr: dict[str, Any]) -> bool:
         """A PR the org did not author: a fork head or a non-member author."""

tests/unit/runtime/test_external_pr_classify.py

@@ -32,3 +32,22 @@ from roboco.runtime.orchestrator import AgentOrchestrator
 )
 def test_is_external_pr(pr: dict[str, object], *, expected: bool) -> None:
     assert AgentOrchestrator._is_external_pr(pr) is expected
+
+
+@pytest.mark.parametrize(
+    ("pr", "allowlist", "expected"),
+    [
+        # Empty allowlist -> every external PR is reviewed (read-only, safe).
+        ({"user_login": "corey"}, set(), True),
+        # Non-empty allowlist gates by GitHub login (case-insensitive).
+        ({"user_login": "corey"}, {"corey"}, True),
+        ({"user_login": "Corey"}, {"corey"}, True),
+        ({"user_login": "mallory"}, {"corey"}, False),
+        ({"user_login": None}, {"corey"}, False),
+        ({}, {"corey"}, False),
+    ],
+)
+def test_pr_author_allowed(
+    pr: dict[str, object], allowlist: set[str], *, expected: bool
+) -> None:
+    assert AgentOrchestrator._pr_author_allowed(pr, allowlist) is expected