feat(web): coquille IDE + arbre de projets unifié (route /ide)

components/ide/ : IdeShell (grille barre d'activité + panneau gauche + zone centrale + dock + barre de statut, splitters persistés, réconciliation des ressources ouvertes contre les données live), ActivityBar (Explorer/Git/Sessions/Groupes + Réglages/Aide), PrimarySidebar, ProjectTree + ProjectTreeNode (arbre unique repos -> worktrees -> sessions, fichiers embarqués via FileTree en mode sans chrome, dépliage paresseux), StatusBar.

Route /ide (layout 'ide'), entrée de nav « IDE », namespace i18n ide (EN/FR). Clics de l'arbre pilotent le store (contexte worktree, ouverture de fichier/terminal). Centre et dock en placeholders (remplis en B4/B5). FileTree gagne un mode embedded. 427 tests.

packages/web/src/components/ide/ActivityBar.vue

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+<template>
+  <nav class="flex w-[var(--ide-activitybar-w)] shrink-0 flex-col items-center gap-1 border-r border-border bg-surface-1 py-2">
+    <button
+      v-for="item in items"
+      :key="item.view"
+      type="button"
+      class="relative flex h-10 w-10 items-center justify-center rounded-lg transition-colors"
+      :class="isActive(item.view) ? 'bg-surface-3 text-fg' : 'text-fg-subtle hover:bg-surface-2 hover:text-fg'"
+      :title="item.label"
+      :aria-label="item.label"
+      @click="ide.toggleActivity(item.view)"
+    >
+      <component :is="item.icon" :size="20" :stroke-width="1.75" />
+      <span
+        v-if="item.badge"
+        class="absolute top-1 right-1 flex h-3.5 min-w-3.5 items-center justify-center rounded-full bg-amber-500 px-1 text-[9px] font-semibold text-amber-950"
+      >
+        {{ item.badge }}
+      </span>
+    </button>
+
+    <div class="mt-auto flex flex-col items-center gap-1">
+      <RouterLink
+        v-for="l in links"
+        :key="l.name"
+        :to="{ name: l.name }"
+        :title="l.label"
+        :aria-label="l.label"
+        class="flex h-10 w-10 items-center justify-center rounded-lg text-fg-subtle transition-colors hover:bg-surface-2 hover:text-fg"
+      >
+        <component :is="l.icon" :size="20" :stroke-width="1.75" />
+      </RouterLink>
+    </div>
+  </nav>
+</template>
+
+<script setup lang="ts">
+import { computed } from 'vue';
+import { useI18n } from 'vue-i18n';
+import { Boxes, FolderTree, GitCompare, LifeBuoy, Settings, SquareTerminal } from '@lucide/vue';
+import { useIdeStore, type ActivityView } from '../../stores/ide';
+import { useNav } from '../../composables/useNav';
+
+const { t } = useI18n();
+const ide = useIdeStore();
+const { waitingCount } = useNav();
+
+const isActive = (v: ActivityView): boolean => ide.activeActivity === v && ide.leftVisible;
+
+const items = computed(() => [
+  { view: 'explorer' as ActivityView, icon: FolderTree, label: t('ide.activity.explorer'), badge: 0 },
+  { view: 'git' as ActivityView, icon: GitCompare, label: t('ide.activity.git'), badge: 0 },
+  { view: 'sessions' as ActivityView, icon: SquareTerminal, label: t('ide.activity.sessions'), badge: waitingCount.value },
+  { view: 'groups' as ActivityView, icon: Boxes, label: t('ide.activity.groups'), badge: 0 },
+]);
+
+const links = computed(() => [
+  { name: 'settings', icon: Settings, label: t('nav.settings') },
+  { name: 'help', icon: LifeBuoy, label: t('nav.help') },
+]);
+</script>