feat(engine): voice pipeline Phase 1 — composition engine and data model

Add the voice pipeline composition engine (D-138 Spike 2, Phase 1):

- voice/prompt_builder.rs: full prompt assembly from culture profile,
  tell state, and base text. Handles occasional injection gating,
  epistemic marker extraction, content-length-gated tell injection.
  16 unit tests.

- blueprint.rs: CultureProfile gains voice_persona, voice_examples,
  occasional_injections fields. NpcBlueprint gains tell_behaviors.
  OccasionalInjection struct with kind discriminator (oath/faith/
  hesitancy/etc), frequency, and tell-suppression gating.

- culture-krenn.ron: v2 voice injector from Spike 1 — persona block,
  3 examples, oath injection at 0.25 frequency.

- D-138 amended: Phi-3 dropped entirely, exact Gemma 2B provenance
  documented. Model file renamed to gemma2.gguf.

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

server/src/npc/blueprint.rs

@@ -22,6 +22,7 @@
 use serde::{Deserialize, Serialize};
 
 use crate::npc::PersonalityTrait;
+use crate::npc::tell_state::TellCategory;
 
 // ---------------------------------------------------------------------------
 // Zone identity specification (input — filled by copy team, ticket #609)
@@ -105,6 +106,16 @@ pub struct CultureProfile {
     pub speech: SpeechPatterns,
     /// Cultural values that bias personality trait selection.
     pub values: CulturalValues,
+    /// Full persona block for voice pipeline LLM prompts (may be absent).
+    #[serde(default)]
+    pub voice_persona: Option<String>,
+    /// Example input/output pairs for voice pipeline prompts.
+    #[serde(default)]
+    pub voice_examples: Vec<VoiceExample>,
+    /// Occasional prompt injections rolled per-prompt by the composition engine.
+    /// Some cultures have none, others several. No cap on count.
+    #[serde(default)]
+    pub occasional_injections: Vec<OccasionalInjection>,
 }
 
 /// Naming conventions for NPC name generation.
@@ -146,6 +157,47 @@ pub struct CulturalValues {
     pub disfavored_traits: Vec<PersonalityTrait>,
 }
 
+// ---------------------------------------------------------------------------
+// Voice pipeline types (D-138, Spike 2)
+// ---------------------------------------------------------------------------
+
+/// Example input/output pair for voice pipeline prompts.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct VoiceExample {
+    /// The input scenario description.
+    pub input: String,
+    /// The expected voiced output.
+    pub output: String,
+}
+
+/// Occasional prompt injection rolled per-prompt by the composition engine.
+///
+/// The model never decides injection frequency — the composition engine rolls
+/// a random check per prompt and either includes the clause or doesn't.
+/// This solves the fundamental problem that small LLMs can't self-gate
+/// vocabulary frequency across independent inference calls.
+///
+/// Different `kind` values represent different categories of injection:
+/// oaths ("void take it"), faith expressions ("God help us"),
+/// verbal hesitancy, greetings ("hey"), etc. The composition engine
+/// treats them uniformly — `kind` exists for human readability and
+/// future filtering.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OccasionalInjection {
+    /// Injection category (e.g. "oath", "faith", "hesitancy", "greeting").
+    pub kind: String,
+    /// LLM instruction text to inject into the prompt.
+    pub clause: String,
+    /// Optional example pair demonstrating the injection in use.
+    #[serde(default)]
+    pub example: Option<VoiceExample>,
+    /// Probability of inclusion per prompt (0.0–1.0).
+    pub frequency: f32,
+    /// Tell categories that suppress this injection to avoid conflicting instructions.
+    #[serde(default)]
+    pub suppress_on_tells: Vec<TellCategory>,
+}
+
 // ---------------------------------------------------------------------------
 // NPC blueprint (output — generator produces these)
 // ---------------------------------------------------------------------------
@@ -169,6 +221,20 @@ pub struct NpcBlueprint {
     pub cultural_markers: CulturalMarkers,
     /// Relationship slots (0-3 per D-024).
     pub relationships: Vec<BlueprintRelationship>,
+    /// Tell-specific behaviors — always passed through verbatim, never re-voiced.
+    #[serde(default)]
+    pub tell_behaviors: Vec<TellBehavior>,
+}
+
+/// A tell-specific behavior string that is passed through verbatim.
+/// Tell behaviors are never re-voiced by the voice pipeline — they are
+/// authored text that plays exactly as written.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TellBehavior {
+    /// Which tell category triggers this behavior.
+    pub category: TellCategory,
+    /// The behavior text shown to the player.
+    pub base_text: String,
 }
 
 /// Cultural markers attached to a generated NPC.
@@ -285,6 +351,9 @@ mod tests {
                 favored_traits: vec![PersonalityTrait::Bold, PersonalityTrait::Honest],
                 disfavored_traits: vec![PersonalityTrait::Reclusive],
             },
+            voice_persona: None,
+            voice_examples: vec![],
+            occasional_injections: vec![],
         };
 
         let ron_str =
@@ -312,6 +381,7 @@ mod tests {
                 relationship_type: "colleague".into(),
                 valence: RelationshipValence::Positive,
             }],
+            tell_behaviors: vec![],
         };
 
         let ron_str =