feat(copy): triangle activation proximity monologue lines (#597)

Author 4 smuggler and 5 detective monologue lines that fire when
the player observes triangle anchor NPCs post-TriangleActivated.

Smuggler (Kael Davan): physical observation → rationalization →
doubt → sensory confirmation. Contracted, personal, friend-arc.

Detective (Sera Venn/Torek): pattern recognition → deviation →
hypothesis → inference → procedural next step. Analytical,
institutional, evidence-cataloguing.

All lines: situation: [triangle_activated], trigger: observe_npc,
cooldown: 9999, priority: 8, prerequisite: npc_in_los: true.

Schema updated: triangle_activated added to situation enum,
npc_in_los added to prerequisites in monologue-pool.schema.json.

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

content/_schema/monologue-pool.schema.json

@@ -75,12 +75,13 @@
               "emergency",
               "routine",
               "observation",
-              "greeting"
+              "greeting",
+              "triangle_activated"
             ]
           },
           "minItems": 1,
           "uniqueItems": true,
-          "description": "D-035 structural tag: situations in which this monologue line is contextually appropriate. 14 v0.1 values. The engine selects using trigger; situation provides additional authoring context for filtering by the caller. NOTE: 'greeting' is not yet in server/src/content/line_pool.rs Situation enum."
+          "description": "D-035 structural tag: situations in which this monologue line is contextually appropriate. 15 v0.1 values (triangle_activated added Sprint 24). The engine selects using trigger; situation provides additional authoring context for filtering by the caller. NOTE: 'greeting' is not yet in server/src/content/line_pool.rs Situation enum."
         },
         "trigger": {
           "type": "string",
@@ -124,6 +125,10 @@
                       "enum": ["unknown", "known", "friendly", "person_of_interest", "hostile"]
                     }
                   }
+                },
+                "npc_in_los": {
+                  "type": "boolean",
+                  "description": "Gate: line only fires when the triggering NPC is in the player's line of sight. Added Sprint 24 for triangle_activated observe_npc lines."
                 }
               }
             }