✨ feat(frontend): système narrateur contextuel avec arc de révélation

Story 3.3 : Textes narrateur contextuels et arc de révélation
- Composable useNarrator.ts avec queue de messages prioritaires
- Composable useIdleDetection.ts (détection inactivité 30s)
- Plugin narrator-transitions.client.ts (déclencheurs de navigation)
- Layout adventure.vue avec NarratorBubble intégré
- Store progression: narratorStage devient un getter calculé (0-20-40-60-80%)
- Pages projets, competences, temoignages, parcours utilisent layout adventure
- Messages: intro, transitions, encouragements 25/50/75%, hints, contact_unlocked

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/app/stores/progression.ts

@@ -11,11 +11,21 @@ export interface ProgressionState {
   easterEggsFound: string[]
   challengeCompleted: boolean
   contactUnlocked: boolean
-  narratorStage: number
   choices: Record<string, string>
   consentGiven: boolean | null
 }
 
+const NARRATOR_STAGE_THRESHOLDS = [0, 20, 40, 60, 80]
+
+function calculateNarratorStage(percent: number): number {
+  for (let i = NARRATOR_STAGE_THRESHOLDS.length - 1; i >= 0; i--) {
+    if (percent >= NARRATOR_STAGE_THRESHOLDS[i]) {
+      return i + 1
+    }
+  }
+  return 1
+}
+
 const SECTIONS = ['projets', 'competences', 'temoignages', 'parcours'] as const
 
 /**
@@ -69,7 +79,6 @@ export const useProgressionStore = defineStore('progression', {
     easterEggsFound: [],
     challengeCompleted: false,
     contactUnlocked: false,
-    narratorStage: 1,
     choices: {},
     consentGiven: null,
   }),
@@ -82,6 +91,8 @@ export const useProgressionStore = defineStore('progression', {
     progressPercent: (state) => Math.round((state.visitedSections.length / SECTIONS.length) * 100),
 
     hasExistingProgress: (state) => state.visitedSections.length > 0 || state.hero !== null,
+
+    narratorStage: (state) => calculateNarratorStage(state.completionPercent),
   },
 
   actions: {
@@ -121,12 +132,6 @@ export const useProgressionStore = defineStore('progression', {
       this.contactUnlocked = true
     },
 
-    updateNarratorStage(stage: number) {
-      if (stage >= 1 && stage <= 5) {
-        this.narratorStage = stage
-      }
-    },
-
     makeChoice(choiceId: string, value: string) {
       this.choices[choiceId] = value
     },