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/ProjectTreeNode.vue

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+<template>
+  <div>
+    <!-- ligne repo (niveau projet) -->
+    <button
+      type="button"
+      class="flex w-full items-center gap-1 rounded px-2 py-1 text-left text-xs text-fg hover:bg-surface-2/60"
+      @click="ide.toggleRepo(repo.id)"
+    >
+      <component :is="repoExpanded ? ChevronDown : ChevronRight" :size="14" class="shrink-0 text-fg-subtle" />
+      <FolderGit2 :size="13" class="shrink-0 text-fg-subtle" />
+      <span class="truncate font-medium">{{ repo.label }}</span>
+      <span v-if="worktreeList.length" class="ml-auto shrink-0 text-[10px] text-fg-subtle">{{ worktreeList.length }}</span>
+    </button>
+
+    <div v-if="repoExpanded" class="pl-3">
+      <p v-if="worktreeList.length === 0" class="px-3 py-0.5 text-[11px] text-fg-subtle">{{ t('ide.noWorktrees') }}</p>
+
+      <div v-for="wt in worktreeList" :key="wt.path">
+        <!-- ligne worktree -->
+        <button
+          type="button"
+          class="flex w-full items-center gap-1 rounded px-2 py-1 text-left text-xs hover:bg-surface-2/60"
+          :class="isActiveWt(wt) ? 'bg-surface-2 text-fg' : 'text-fg-muted'"
+          @click="onWtClick(wt)"
+        >
+          <component :is="isWtExpanded(wt) ? ChevronDown : ChevronRight" :size="14" class="shrink-0 text-fg-subtle" />
+          <component :is="wt.isMain ? Home : GitBranch" :size="12" class="shrink-0 text-fg-subtle" />
+          <span class="truncate font-mono">{{ wt.branch ?? wt.head.slice(0, 7) }}</span>
+          <span v-if="isDirty(wt)" class="ml-auto shrink-0 text-amber-400" :title="t('worktrees.dirty', { n: wt.git.dirtyCount })">●</span>
+        </button>
+
+        <!-- sessions live corrélées au worktree (par cwd) -->
+        <button
+          v-for="s in sessionsFor(wt)"
+          :key="s.id"
+          type="button"
+          class="flex w-full items-center gap-1.5 rounded py-0.5 pr-2 pl-9 text-left text-[11px] hover:bg-surface-2/60"
+          :class="ide.activeDockSessionId === s.id ? 'bg-surface-2 text-fg' : 'text-fg-muted'"
+          @click="ide.openTerminal(s.id)"
+        >
+          <SessionStateBadge :session="s" />
+          <span class="truncate font-mono">{{ s.command }}</span>
+        </button>
+
+        <!-- fichiers du worktree (arbre embarqué, chargé paresseusement au dépliage) -->
+        <div v-if="isWtExpanded(wt)" class="pl-4">
+          <FileTree
+            :wt="wt.path"
+            :active="activeFileFor(wt)"
+            embedded
+            :depth="0"
+            @open="(rel) => ide.openFile(wt.repoId, wt.path, rel)"
+          />
+        </div>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed } from 'vue';
+import { useI18n } from 'vue-i18n';
+import { ChevronDown, ChevronRight, FolderGit2, GitBranch, Home } from '@lucide/vue';
+import type { RepoSummary, SessionSummary, WorktreeSummary } from '@arboretum/shared';
+import { useIdeStore } from '../../stores/ide';
+import { useWorktreesStore } from '../../stores/worktrees';
+import { useSessionsStore } from '../../stores/sessions';
+import FileTree from '../workspace/FileTree.vue';
+import SessionStateBadge from '../SessionStateBadge.vue';
+
+const props = defineProps<{ repo: RepoSummary }>();
+const { t } = useI18n();
+const ide = useIdeStore();
+const worktrees = useWorktreesStore();
+const sessions = useSessionsStore();
+
+const repoExpanded = computed(() => ide.expandedRepoIds.includes(props.repo.id));
+const worktreeList = computed(() => worktrees.worktreesForRepo(props.repo.id));
+
+const isWtExpanded = (wt: WorktreeSummary): boolean => ide.expandedWtPaths.includes(wt.path);
+const isActiveWt = (wt: WorktreeSummary): boolean =>
+  ide.activeContext?.repoId === wt.repoId && ide.activeContext?.wtPath === wt.path;
+const isDirty = (wt: WorktreeSummary): boolean => wt.git.dirtyCount > 0;
+
+// sessions vivantes dont le cwd correspond au worktree (corrélation par répertoire).
+function sessionsFor(wt: WorktreeSummary): SessionSummary[] {
+  return sessions.sessions.filter((s) => s.live && s.cwd === wt.path);
+}
+
+// fichier actif si l'onglet éditeur courant appartient à ce worktree.
+function activeFileFor(wt: WorktreeSummary): string | null {
+  const tab = ide.activeTab;
+  return tab && tab.repoId === wt.repoId && tab.wtPath === wt.path ? tab.file : null;
+}
+
+function onWtClick(wt: WorktreeSummary): void {
+  ide.setActiveWorktree(wt.repoId, wt.path);
+  ide.toggleWt(wt.path);
+}
+</script>