refactor: rename CloudEvents extension attributes hub* → central*

Rename extension attributes for consistency with project naming:
- hubschemaversion → centralschemaversion
- hubcategory → centralcategory
- hubseverity → centralseverity

Non-breaking change - no consumers depend on these names yet.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/central/cloudevents_wire.py

@@ -24,13 +24,13 @@ def wrap_event(event: Event, config: Config) -> tuple[dict[str, Any], str]:
 
     # Build extension attributes - lowercase, no underscores per CE spec
     extensions: dict[str, Any] = {
-        "hubschemaversion": config.cloudevents.schema_version,
+        "centralschemaversion": config.cloudevents.schema_version,
-        "hubcategory": event.category,
+        "centralcategory": event.category,
     }
 
-    # Only include hubseverity if severity is present
+    # Only include centralseverity if severity is present
     if event.severity is not None:
-        extensions["hubseverity"] = event.severity
+        extensions["centralseverity"] = event.severity
 
     # Create CloudEvent
     ce = CloudEvent(

tests/test_models.py

@@ -129,19 +129,19 @@ class TestCloudEventsWire:
         envelope, _ = wrap_event(sample_event, sample_config)
 
         # Check that extension attributes exist and are lowercase
-        assert envelope["hubschemaversion"] == "1.0"
+        assert envelope["centralschemaversion"] == "1.0"
-        assert envelope["hubcategory"] == "wx.alert.severe_thunderstorm_warning"
+        assert envelope["centralcategory"] == "wx.alert.severe_thunderstorm_warning"
-        assert envelope["hubseverity"] == 3
+        assert envelope["centralseverity"] == 3
 
         # Verify no uppercase or underscores in extension names
-        for key in ["hubschemaversion", "hubcategory", "hubseverity"]:
+        for key in ["centralschemaversion", "centralcategory", "centralseverity"]:
             assert key.islower()
             assert "_" not in key
 
-    def test_severity_none_omits_hubseverity(
+    def test_severity_none_omits_centralseverity(
         self, sample_geo: Geo, sample_config: Config
     ) -> None:
-        """When severity is None, hubseverity is omitted entirely."""
+        """When severity is None, centralseverity is omitted entirely."""
         event = Event(
             id="test-no-severity",
             source="test",
@@ -154,8 +154,8 @@ class TestCloudEventsWire:
 
         envelope, _ = wrap_event(event, sample_config)
 
-        # hubseverity should not be present at all
+        # centralseverity should not be present at all
-        assert "hubseverity" not in envelope
+        assert "centralseverity" not in envelope
         # Other extensions should still be present
-        assert "hubschemaversion" in envelope
+        assert "centralschemaversion" in envelope
-        assert "hubcategory" in envelope
+        assert "centralcategory" in envelope