P1 complete: web front, test suite, CI — acceptance ALL GREEN

Fan-out integration + fixes found by the test/acceptance pass:
- FIX ring-buffer: chunks >= capacity skipped bytes now count into the
  monotonic offset (invariant: stream byte k lives at k % capacity) —
  window order was corrupted on unaligned big chunks
- FIX auth: non-numeric cookie expiry no longer bypasses expiration
- FIX protocol: safe-integer validation on ack.bytes / hello.protocol
- FIX @fastify/websocket v11: websocket route must be registered in an
  encapsulated context after plugin load (handler got REST signature)
- FIX flow-control deadlock found by e2e acceptance: client only ACKs
  on data receipt, so pausing with an unACKed residue in (LOW,
  ACK_EVERY] stalled both sides at 0.9 MB. ACK_EVERY now 64 KiB (<=
  LOW invariant, tested) + trailing debounced ACK in the web client
- Web: Vue 3 + Vite + Pinia + Tailwind 4 + vue-i18n (EN/FR) + xterm 6
  (fit + webgl fallback), multiplexed ws-client with reconnect/backoff
  and resync epochs
- Tests: 100 vitest (protocol fuzz, ring edges, auth, pty-manager flow
  control with mocked pty, REST e2e) ; CI Node 22/24 + pack-smoke
- scripts/acceptance-p1.mjs: real daemon + real WS client — boot,
  login, attach, stdin, 10 MB flood w/ ACK (13.7 MB/1.9s, RSS bounded),
  brutal disconnect + replay resync, kill broadcast, SIGTERM drain

packages/web/src/views/SessionView.vue

@@ -0,0 +1,40 @@
+<template>
+  <div class="flex min-h-0 flex-col">
+    <header class="flex items-center gap-3 border-b border-zinc-800 bg-zinc-900/60 px-3 py-1.5">
+      <RouterLink :to="{ name: 'sessions' }" class="text-sm text-zinc-400 transition-colors hover:text-zinc-200">
+        ← {{ t('terminal.back') }}
+      </RouterLink>
+      <span v-if="session" class="badge bg-zinc-800 font-mono text-zinc-300">{{ session.command }}</span>
+      <span class="truncate font-mono text-xs text-zinc-500" :title="session?.cwd ?? sessionId">
+        {{ session?.cwd ?? sessionId }}
+      </span>
+      <div class="ml-auto">
+        <LanguageSwitcher />
+      </div>
+    </header>
+    <TerminalView :key="`${sessionId}:${mode}`" :session-id="sessionId" :mode="mode" class="flex-1" />
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed, onMounted } from 'vue';
+import { useRoute } from 'vue-router';
+import { useI18n } from 'vue-i18n';
+import { useSessionsStore } from '../stores/sessions';
+import TerminalView from '../components/TerminalView.vue';
+import LanguageSwitcher from '../components/LanguageSwitcher.vue';
+
+const { t } = useI18n();
+const route = useRoute();
+const store = useSessionsStore();
+
+const sessionId = computed(() => String(route.params.id));
+const mode = computed<'interactive' | 'observer'>(() => (route.query.mode === 'observer' ? 'observer' : 'interactive'));
+const session = computed(() => store.sessions.find((s) => s.id === sessionId.value) ?? null);
+
+onMounted(() => {
+  // navigation directe : la liste n'est pas encore chargée (en-tête cwd/commande)
+  if (store.sessions.length === 0) void store.fetchSessions();
+  store.startRealtime();
+});
+</script>