chore(simulation): address review suggestions — comments and minor fixes

- monologue.rs: tracing::warn on unrecognized trigger in fallback arm
- disclosure.rs: borrow-sequencing comment, first() simplification note
- trait_modifiers.rs: delegate parse_confidence to KnowledgeConfidence::try_from
- npc_knowledge_transfer.rs: fix misleading "draw randomly" comment,
  document one-directional transfer behavior
- graph.rs: document intentional no-retrigger after contradiction
- dialogue.rs: explain entity grant guardrail asymmetry (D-079)
- knowledge/mod.rs: document one-tick monologue lag from system ordering
- poi_discovery.rs: document D-079 carve-out for direct KG write

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

server/src/simulation/monologue.rs

@@ -457,7 +457,10 @@ fn select_hardcoded_fallback(trigger: &str, rng: &mut impl Rng) -> (String, Stri
         "hear_sound" => HEAR_SOUND_LINES,
         "witness_interaction" => WITNESS_INTERACTION_LINES,
         "post_conversation" => POST_CONVERSATION_LINES,
-        _ => OBSERVE_NPC_LINES,
+        unknown => {
+            tracing::warn!("select_hardcoded_fallback: unrecognized trigger '{}', using observe_npc", unknown);
+            OBSERVE_NPC_LINES
+        }
     };
     let index = rng.random_range(0..lines.len());
     (lines[index].0.to_string(), lines[index].1.to_string())