feat(groups): session Claude unique par groupe via --add-dir (P6)

Un groupe lance désormais UNE seule session Claude couvrant tous ses
repos/worktrees (--add-dir) au lieu d'une session par repo, pour
travailler en simultané dans une conversation partagée. Le transport WS,
le flow control et l'attach sont inchangés (toujours 1 session, 1 channel).

- shared: SessionSummary.addedDirs/groupId (champs additifs optionnels) ;
  CreateGroupSessionRequest / GroupSessionResponse.
- server: --add-dir dans claude-launcher ; spawn({addDirs,groupId}) +
  persistance (migration #8 : sessions.added_dirs/group_id) ;
  POST /api/v1/groups/:id/session (résolution des dirs cote serveur) ;
  resume re-relie les dirs ; deleteGroup nullifie group_id.
- web: GroupSessionModal (modes feature / checkouts principaux) ;
  createGroupFeature/createGroupSession ; badge « groupe · N depots » ;
  sessionsInGroup dedupliquee.
- site: textes EN/FR « une seule session Claude » + diagramme hub.
- tests: claude-launcher, pty-manager (groupe), group-manager ;
  acceptation P5 etendue (session de groupe multi-repo). 272 tests verts.

packages/web/src/components/GroupSessionModal.vue

@@ -0,0 +1,148 @@
+<template>
+  <div class="fixed inset-0 z-50 flex items-center justify-center bg-black/60 p-4" @click.self="emit('close')">
+    <div class="flex max-h-[90vh] w-full max-w-lg flex-col gap-3 overflow-y-auto rounded-lg border border-zinc-800 bg-zinc-900 p-4">
+      <header class="flex items-center gap-2">
+        <h2 class="font-semibold text-zinc-100">{{ t('crossRepo.title') }}</h2>
+        <button class="btn ml-auto text-xs" @click="emit('close')">{{ t('crossRepo.close') }}</button>
+      </header>
+      <p class="text-xs text-zinc-500">{{ t('crossRepo.intro') }}</p>
+
+      <form class="flex flex-col gap-3" @submit.prevent="onSubmit">
+        <!-- mode : couvrir une nouvelle branche par repo, ou les checkouts principaux -->
+        <div class="flex flex-col gap-1 text-xs text-zinc-400">
+          {{ t('crossRepo.modeLabel') }}
+          <div class="flex flex-wrap gap-3">
+            <label class="flex items-center gap-1.5">
+              <input v-model="mode" type="radio" value="feature" :disabled="running" /> {{ t('crossRepo.modeFeature') }}
+            </label>
+            <label class="flex items-center gap-1.5">
+              <input v-model="mode" type="radio" value="main" :disabled="running" /> {{ t('crossRepo.modeMain') }}
+            </label>
+          </div>
+        </div>
+
+        <!-- mode feature : branche commune créée dans chaque repo -->
+        <template v-if="mode === 'feature'">
+          <label class="flex flex-col gap-1 text-xs text-zinc-400">
+            {{ t('crossRepo.branchLabel') }}
+            <input v-model="branch" class="input font-mono" :placeholder="t('crossRepo.branchPlaceholder')" :required="mode === 'feature'" />
+          </label>
+          <div class="flex flex-wrap items-end gap-3">
+            <label class="flex items-center gap-1.5 text-xs text-zinc-400">
+              <input v-model="newBranch" type="checkbox" /> {{ t('crossRepo.newBranch') }}
+            </label>
+            <label class="flex flex-col gap-1 text-xs text-zinc-400">
+              {{ t('crossRepo.baseRefLabel') }}
+              <input v-model="baseRef" class="input font-mono" placeholder="HEAD" />
+            </label>
+          </div>
+        </template>
+
+        <label class="flex flex-col gap-1 text-xs text-zinc-400">
+          {{ t('crossRepo.commandLabel') }}
+          <select v-model="command" class="input">
+            <option value="claude">claude</option>
+            <option value="bash">bash</option>
+          </select>
+        </label>
+
+        <div class="flex flex-col gap-1 text-xs text-zinc-400">
+          {{ t('crossRepo.reposLabel') }}
+          <div class="flex flex-col gap-1">
+            <div
+              v-for="repo in repos"
+              :key="repo.id"
+              class="flex items-center gap-2 rounded border border-zinc-800 bg-zinc-950/40 px-2 py-1"
+            >
+              <span class="flex-1 text-zinc-300">{{ repo.label }}</span>
+              <span v-if="repoStatus(repo.id)" class="text-[11px]" :class="repoStatusClass(repo.id)">
+                {{ repoStatus(repo.id) }}
+              </span>
+            </div>
+          </div>
+        </div>
+
+        <p v-if="outcome" class="text-xs" :class="outcome.session ? 'text-emerald-400' : 'text-red-400'">
+          {{ outcome.session ? t('crossRepo.done') : t('crossRepo.sessionFailed') }}
+        </p>
+        <p v-if="errorMsg" class="text-xs text-red-400">{{ errorMsg }}</p>
+
+        <div class="flex items-center gap-2">
+          <button type="submit" class="btn-primary" :disabled="running || (mode === 'feature' && branch.trim() === '') || repos.length === 0">
+            {{ running ? t('crossRepo.launching') : t('crossRepo.launch') }}
+          </button>
+        </div>
+      </form>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed, ref } from 'vue';
+import { useI18n } from 'vue-i18n';
+import type { RepoSummary } from '@arboretum/shared';
+import { useGroupsStore, type CrossRepoResult, type GroupFeatureOutcome } from '../stores/groups';
+
+const props = defineProps<{ groupId: string; repos: RepoSummary[] }>();
+const emit = defineEmits<{ close: [] }>();
+
+const { t } = useI18n();
+const groups = useGroupsStore();
+
+const mode = ref<'feature' | 'main'>('feature');
+const branch = ref('');
+const newBranch = ref(true);
+const baseRef = ref('');
+const command = ref<'claude' | 'bash'>('claude');
+const wtResults = ref<Record<string, CrossRepoResult>>({});
+const outcome = ref<GroupFeatureOutcome | null>(null);
+const errorMsg = ref<string | null>(null);
+const running = ref(false);
+
+const skippedById = computed<Record<string, string>>(() => {
+  const m: Record<string, string> = {};
+  for (const s of outcome.value?.skipped ?? []) m[s.repoId] = s.reason;
+  return m;
+});
+
+function repoStatus(repoId: string): string {
+  const wt = wtResults.value[repoId];
+  if (wt) return wt.status === 'ok' ? t('crossRepo.ok') : `${t('crossRepo.error')}: ${wt.message ?? ''}`;
+  const skip = skippedById.value[repoId];
+  if (skip) return `${t('crossRepo.skippedLabel')}: ${skip}`;
+  return '';
+}
+function repoStatusClass(repoId: string): string {
+  const wt = wtResults.value[repoId];
+  if (wt) return wt.status === 'ok' ? 'text-emerald-400' : 'text-red-400';
+  return skippedById.value[repoId] ? 'text-amber-400' : '';
+}
+
+async function onSubmit(): Promise<void> {
+  if (running.value || props.repos.length === 0) return;
+  if (mode.value === 'feature' && branch.value.trim() === '') return;
+  running.value = true;
+  wtResults.value = {};
+  outcome.value = null;
+  errorMsg.value = null;
+  try {
+    outcome.value = await groups.createGroupFeature(
+      props.groupId,
+      props.repos.map((r) => r.id),
+      {
+        command: command.value,
+        ...(mode.value === 'feature'
+          ? { branch: branch.value.trim(), newBranch: newBranch.value, ...(baseRef.value.trim() ? { baseRef: baseRef.value.trim() } : {}) }
+          : {}),
+      },
+      (result) => {
+        wtResults.value = { ...wtResults.value, [result.repoId]: result };
+      },
+    );
+  } catch (err) {
+    errorMsg.value = err instanceof Error ? err.message : String(err);
+  } finally {
+    running.value = false;
+  }
+}
+</script>