feat: online verification, node removals, and knowledge browser

Adds claim-bound online evidence records and citation verification scripts,
node removal transport/adapter, retrieval benchmark and owner-review tooling,
GraphCanvas/SourceDetail knowledge browser UI, and the ingest handoff helper.
Bumps the agents/gewu pack to the online-verification branch.

tests/test_prepare_four_file_run.py

@@ -0,0 +1,52 @@
+import subprocess
+
+import pytest
+from scripts.prepare_four_file_run import prepare
+
+
+def test_preparation_fails_closed_on_dirty_source_checkout(tmp_path):
+    repo = tmp_path / "source"
+    repo.mkdir()
+    subprocess.run(["git", "init", str(repo)], check=True, capture_output=True)
+    subprocess.run(
+        ["git", "-C", str(repo), "config", "user.email", "benchmark@example.invalid"],
+        check=True,
+    )
+    subprocess.run(
+        ["git", "-C", str(repo), "config", "user.name", "Benchmark Test"], check=True
+    )
+    (repo / "tracked.txt").write_text("baseline\n")
+    subprocess.run(["git", "-C", str(repo), "add", "tracked.txt"], check=True)
+    subprocess.run(["git", "-C", str(repo), "commit", "-m", "baseline"], check=True)
+    (repo / "untracked.txt").write_text("dirty\n")
+
+    with pytest.raises(ValueError, match="must be clean"):
+        prepare(
+            repo=repo,
+            source_data=tmp_path / "source-data",
+            sources=[],
+            reference=tmp_path / "reference.json",
+            extractions=tmp_path / "extractions",
+            model_id="pinned-model@revision",
+            search_mode="keyword",
+            budget_tokens=8000,
+            output_root=tmp_path / "run",
+            commit="HEAD",
+        )
+
+    assert not (tmp_path / "run").exists()
+
+
+def test_private_tree_removes_group_and_world_permissions(tmp_path):
+    from scripts.prepare_four_file_run import private_tree
+
+    root = tmp_path / "private"
+    root.mkdir(mode=0o755)
+    child = root / "data.txt"
+    child.write_text("private")
+    child.chmod(0o644)
+
+    private_tree(root)
+
+    assert root.stat().st_mode & 0o077 == 0
+    assert child.stat().st_mode & 0o077 == 0