feat(simulation): add proximity detection and interaction verbs

Implement compute_nearby_interactions system that detects entities
within close (≤2) and mid (≤5) Manhattan distance, computes
available verbs per D-060 spec. NPCs get Talk+Observe at close
range, Observe-only at mid range; PersonOfInterest flips priority.
Objects get Examine. Results populate nearby_interactions[] on
ObserverSnapshot v4. Bump protocol version 3→4. Implements #404.

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

server/src/bridge/mod.rs

@@ -102,7 +102,8 @@ pub fn generate_snapshot(
         day: time.day(),
         time_of_day: time.time_of_day_minutes(),
         day_phase: time.day_phase(),
-        paused: time.paused,
+        paused: time.paused(),
+        tick_rate: time.tick_rate,
     };
 
     tracing::trace!(
@@ -111,12 +112,13 @@ pub fn generate_snapshot(
         visible.len()
     );
     buffer.snapshot = Some(ObserverSnapshot {
-        version: 3,
+        version: 4,
         tick: time.tick,
         game_time,
         player_facing: FacingDirection::default(),
         entities: visible,
         visible_tiles: Vec::new(), // Empty until #112 adds LOS filtering
+        nearby_interactions: Vec::new(),
     });
 }
 

server/src/bridge/types.rs

@@ -6,18 +6,19 @@ use bevy_ecs::prelude::*;
 use serde::{Deserialize, Serialize};
 
 pub use crate::knowledge::types::{EntityVisibility, KnowledgeConfidence, RelationshipState};
-pub use crate::simulation::time::DayPhase;
+pub use crate::simulation::time::{DayPhase, TickRate};
 
 /// The ONLY data structure crossing the client-server boundary (D-020)
 /// Contains all information visible to the observer at a given tick.
 ///
 /// v2 adds: game_time, player_facing, visible_tiles, visibility sectors.
 /// v3 adds: relationship (D-033 entity color), observation (Visible/Remembered).
+/// v4 adds: nearby_interactions (D-060, #404 proximity + verbs[]).
 /// Future fields: ambient sound events, internal monologue triggers,
 /// HUD state (D-020 expansion).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ObserverSnapshot {
-    /// Protocol version for forward compatibility. Current: 3.
+    /// Protocol version for forward compatibility. Current: 4.
     pub version: u8,
     /// Simulation tick when this snapshot was produced
     pub tick: u64,
@@ -29,6 +30,10 @@ pub struct ObserverSnapshot {
     pub entities: Vec<VisibleEntity>,
     /// Tiles visible to the observer for fog rendering
     pub visible_tiles: Vec<VisibleTile>,
+    /// Entities within interaction range with available verbs (D-060, #404).
+    /// Sorted by distance (nearest first). v0.1 client reads verbs[0] on the nearest entity.
+    #[serde(default)]
+    pub nearby_interactions: Vec<NearbyInteraction>,
 }
 
 /// Game time data for client display (D-031)
@@ -41,8 +46,11 @@ pub struct GameTime {
     pub time_of_day: u64,
     /// Current day phase (Morning/Afternoon/Evening/Night)
     pub day_phase: DayPhase,
-    /// Whether simulation is paused
+    /// Whether simulation is paused (tick_rate == Paused)
     pub paused: bool,
+    /// Current tick rate state (D-052)
+    #[serde(default)]
+    pub tick_rate: TickRate,
 }
 
 /// 8-directional facing direction, matching movement system.
@@ -136,6 +144,45 @@ pub enum PlayerAction {
     UsePerceptionMode(String),
     Pause,
     Unpause,
+    /// Set tick rate: Full (1.0), Half (0.5), or Paused (0.0) per D-052
+    SetTickRate(TickRate),
+}
+
+/// Available interaction verbs for a nearby entity (D-060, #404)
+/// Embedded in ObserverSnapshot.nearby_interactions.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct NearbyInteraction {
+    /// Wire-format entity identifier
+    pub entity_id: u64,
+    /// Entity type for client-side verb display
+    pub entity_type: EntityKind,
+    /// Manhattan distance from player
+    pub distance: f32,
+    /// Available verbs sorted by priority (index 0 = highest priority)
+    pub verbs: Vec<VerbOption>,
+}
+
+/// A single available verb on a nearby entity
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct VerbOption {
+    /// Verb type
+    pub kind: VerbKind,
+    /// Display label for the context prompt (e.g. "Talk", "Observe", "Examine")
+    pub label: String,
+    /// Priority rank (lower = higher priority). v0.1 client reads only priority 1.
+    pub priority: u8,
+    /// Whether this verb is currently available (false = greyed out in v0.2)
+    pub available: bool,
+}
+
+/// Verb types for the interaction system (D-060)
+/// Only active verbs appear in verbs[]. Passive (Look, Overhear) and
+/// reactive (Monologue) verbs fire independently.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub enum VerbKind {
+    ExamineObject,
+    ExamineNpc,
+    Talk,
 }
 
 /// Snapshot buffer resource for staging outgoing ObserverSnapshots