feat(engine): retire D-078 overheard conversation system (#848)

Per R-012: delete conversation.rs, both overheard content files, and
remove all 6 wire-up points (social_plugin, bridge/types, monologue,
voice/integration). Protocol version 22 → 23. Scope confirmed by
#842 audit — npc/ and content/global/ untouched. Surviving NPC
components (NpcName, NpcColorIndex, NpcConversation) migrated to
simulation/npc_components.rs for use by D-080 knowledge propagation.
Also applies pre-existing cargo fmt debt (names.rs and 4 others).

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

server/src/bridge/debug.rs

@@ -14,9 +14,9 @@ use crate::bridge::types::{
 };
 use crate::knowledge::EntityRegistry;
 use crate::npc::Npc;
-use crate::simulation::conversation::NpcName;
 use crate::simulation::economy::{EconSimResource, EconStateResource};
 use crate::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
+use crate::simulation::npc_components::NpcName;
 use crate::simulation::tier::ActiveSim;
 use crate::simulation::time::SimulationTime;
 use crate::simulation::triangle::TriangleState;

server/src/bridge/mod.rs

@@ -244,7 +244,6 @@ impl Plugin for BridgePlugin {
                     crate::simulation::monologue::trigger_event_monologue
                         .after(crate::simulation::monologue::process_sprint_anomaly_monologue)
                         .after(crate::simulation::sound::collect_sound_events)
-                        .after(crate::simulation::conversation::run_npc_conversations)
                         .after(crate::simulation::dialogue::process_walk_away),
                     crate::simulation::monologue::process_contradiction_monologue
                         .after(crate::simulation::monologue::trigger_event_monologue),

server/src/bridge/text_renderer.rs

@@ -304,8 +304,7 @@ mod tests {
             dialogue_response: None,
             blocked_entities: vec![],
             scan_events: vec![],
-            conversation_events: vec![],
-            conversation_ended: vec![],
+
             follow_state: None,
             character_pressure: None,
             sound_events: vec![],
@@ -447,8 +446,7 @@ mod tests {
             dialogue_response: None,
             blocked_entities: vec![],
             scan_events: vec![],
-            conversation_events: vec![],
-            conversation_ended: vec![],
+
             follow_state: None,
             character_pressure: None,
             sound_events: vec![],

server/src/bridge/types.rs

@@ -17,7 +17,7 @@ pub use crate::simulation::time::{DayPhase, TickRate};
 /// negotiation is unnecessary. Client should reject snapshots with version !=
 /// PROTOCOL_VERSION. New fields use #[serde(default)] only during the migration
 /// period, then the default is removed once both sides are updated.
-pub const PROTOCOL_VERSION: u8 = 22;
+pub const PROTOCOL_VERSION: u8 = 23;
 
 /// Handshake message sent as the very first framed message after connection (#555).
 /// Client reads this before entering the normal tick loop and validates
@@ -85,6 +85,7 @@ pub struct StartupMessage {
 ///           EconStateQuery PlayerAction variant (#822).
 /// v22 adds: bookmark_catalog (#614, D-115/D-117 CK3-style bookmark system),
 ///           RequestBookmarkCatalog + ConfirmBookmark PlayerAction variants (#614).
+/// v23 removes: conversation_events, conversation_ended (D-078 scrapped per R-012).
 /// Future fields: ambient sound events, HUD state (D-020 expansion).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ObserverSnapshot {
@@ -142,15 +143,6 @@ pub struct ObserverSnapshot {
     /// Empty when no sounds are in range.
     #[serde(default)]
     pub sound_events: Vec<crate::simulation::sound::SoundEvent>,
-    /// Overheard NPC-to-NPC conversation lines this tick (#247, D-078).
-    /// Each event carries pre-occluded text — client renders verbatim.
-    /// Empty when no conversations are overheard.
-    #[serde(default)]
-    pub conversation_events: Vec<crate::simulation::conversation::ConversationEvent>,
-    /// Conversations that ended this tick (#247, D-078).
-    /// Client dismisses the passive dialogue panel for these pairs.
-    #[serde(default)]
-    pub conversation_ended: Vec<crate::simulation::conversation::ConversationEndEvent>,
     /// Follow-mode state for client HUD display (#241).
     /// Present when the player is actively following an NPC.
     /// Client shows follow indicator with distance, LOS, and tension.