feat: scoped threshold-config merge for non-admin saves

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NfPpSpccTWBfZg1FTveyaU

tests/test_config_access.py

@@ -190,3 +190,58 @@ def test_merge_hosts_rejects_unknown_fields():
 def test_merge_hosts_owner_clearing_list_removes_key():
     result = _merge_hosts(_full_payload(mine={"owner": "alice", "watch": True}))
     assert "notification_channels" not in result["mine"]
+
+
+# ---------------------------------------------------------------------------
+# merge_threshold_configs_scoped
+# ---------------------------------------------------------------------------
+
+MERGE_EXISTING_TCS = {
+    "default": {"thresholds": {"cpu": {"load": {"warning": 2}}}},
+    "alice_tc": {"owner": "alice", "thresholds": {"cpu": {"load": {"warning": 3}}}},
+    "bob_tc": {"owner": "bob", "thresholds": {}},
+    "global_tc": {"thresholds": {}},
+}
+
+
+def _merge_tcs(payload):
+    return ca.merge_threshold_configs_scoped(dict(MERGE_EXISTING_TCS), payload, "alice")
+
+
+def test_merge_tcs_new_config_owner_forced():
+    result = _merge_tcs({"alice_tc": {"thresholds": {}},
+                         "new_tc": {"thresholds": {}, "owner": "bob"}})
+    assert result["new_tc"]["owner"] == "alice"
+
+
+def test_merge_tcs_edit_own():
+    result = _merge_tcs({"alice_tc": {"thresholds": {"mem": {"used": {"warning": 90}}}}})
+    assert result["alice_tc"]["thresholds"] == {"mem": {"used": {"warning": 90}}}
+    assert result["alice_tc"]["owner"] == "alice"
+
+
+def test_merge_tcs_delete_own_when_missing():
+    result = _merge_tcs({})
+    assert "alice_tc" not in result
+
+
+def test_merge_tcs_preserves_global_and_foreign():
+    result = _merge_tcs({"alice_tc": {"thresholds": {}}})
+    assert result["default"] == MERGE_EXISTING_TCS["default"]
+    assert result["bob_tc"] == MERGE_EXISTING_TCS["bob_tc"]
+    assert result["global_tc"] == MERGE_EXISTING_TCS["global_tc"]
+
+
+def test_merge_tcs_rejects_default():
+    with pytest.raises(ca.ScopedMergeError, match="default"):
+        _merge_tcs({"alice_tc": {"thresholds": {}}, "default": {"thresholds": {}}})
+
+
+def test_merge_tcs_rejects_global_name_collision():
+    with pytest.raises(ca.ScopedMergeError, match="global_tc"):
+        _merge_tcs({"alice_tc": {"thresholds": {}}, "global_tc": {"thresholds": {}}})
+
+
+def test_merge_tcs_rejects_foreign_owned():
+    with pytest.raises(ca.ScopedMergeError, match="bob_tc"):
+        _merge_tcs({"alice_tc": {"thresholds": {}}, "bob_tc": {"thresholds": {}}})