feat(simulation): add NPC name masking with role labels and color index

Server-side infrastructure for information asymmetry in dialogue.
NPCs display role labels (Worker, Supervisor, Patron) instead of
real names until the player explicitly learns them via KG lookup.
NpcColorIndex (stable_id % 8) persists across name reveal.

ConversationEvent and DialogueResponseEvent carry display names +
color indices on the wire with serde(default) for compat.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/bridge/text_renderer.rs

@@ -363,6 +363,8 @@ mod tests {
             line_id: "line_test".into(),
             text: "Welcome to the docks.".into(),
             speaker_entity_id: 100,
+            speaker_color_index: 0,
+            speaker_name: "Dock Worker".into(),
         });
         let text = format_snapshot_text(&snap);
         assert!(text.contains("Dialogue: [npc:100] \"Welcome to the docks.\""));