feat(realtime): full Fase 2b.0 test suite + infra hardening

Extend the 2b.0 red-phase coverage: presence, RLS isolation, offline-queue
contract, and Playwright scaffolds for the shopping-session UX. Only the
presence test is blocked on an upstream Realtime bug (documented below); all
other Realtime paths are proven end-to-end.

Tests
- realtime-postgres-changes.test.ts: now uses afterEach socket disconnect
  (Vitest singleFork kept Phoenix sockets alive between files, leaking state)
- realtime-isolation.test.ts (new): R-I-01 David (guest, same collective)
  receives events; R-I-02 Eva (non-member) receives NONE — RLS is enforced
  server-side per subscribed JWT
- realtime-presence.test.ts (new, describe.skip): two-client roster + leave
  assertions ready, gated on upstream bug
- sync-queue.test.ts (new, describe.skip): 7 placeholders pinning the
  apps/web/src/lib/sync/queue.ts contract (Q-01..Q-04 enqueue / in-order
  flush / retry; F-01..F-03 online-event flush + last-write-wins)
- apps/web/tests/e2e/{session,realtime,offline}.test.ts (new, describe.skip):
  S-01..S-03, R-E-01, R-E-02, O-01, O-02 pinning the Modo Compra UI contract
- vitest.config.ts: fileParallelism=false, drop singleFork so each file gets
  a fresh worker fork — prevents RealtimeClient singleton leakage

Infra
- db-init/00-role-passwords.sh: pre-create `realtime` schema with
  AUTHORIZATION supabase_admin. Realtime's per-tenant migrator creates tables
  INSIDE the schema but does not create the schema itself; without this the
  first tenant connect fails with "schema realtime does not exist"
- docker-compose.dev.yml: adopt the upstream supabase/supabase Realtime env
  shape — SEED_SELF_HOST=true + RUN_JANITOR=true + RLIMIT_NOFILE=10000 +
  drop the custom `command: eval seeds` (that bypasses the normal supervisor
  startup and was observed to cause GenServer crashes under load).
  Version pinned to v2.76.5 to match the official docker-compose.

Known upstream bug
- Realtime v2.76.5 and v2.83.0 both crash on presence_diff:
  `(UndefinedFunctionError) RealtimeChannel.handle_out/3 is undefined`.
  postgres_changes + isolation unaffected (they don't traverse handle_out).
  Presence tests stay `describe.skip` until a fixed upstream is released.

Totals: 59 Vitest passed (+ 9 skipped awaiting implementation/upstream),
16 pgTAP, 15 Playwright (+ 7 E2E scaffolded for 2b UI) = 90 green.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/tests/e2e/offline.test.ts

@@ -0,0 +1,24 @@
+/**
+ * O-series — Fase 2b.2 (offline-first)
+ *
+ * Verifies the optimistic queue + post-reconnect flush flow. Uses Playwright's
+ * `context.setOffline(true)` to simulate a dropped connection. Skipped until
+ * the sync module + offline banner exist.
+ */
+import { test } from '@playwright/test';
+
+test.describe.skip('Offline queue + reconnect flush (pending sync module)', () => {
+	test('O-01: mutations while offline stay locally and show the "offline" banner', async () => {
+		// Given Borja is on /lists/[id] with real network
+		// When context.setOffline(true) + add two items
+		// Then both items render locally and a "sin conexión / offline" banner is visible
+	});
+
+	test('O-02: going back online flushes pending_ops and hides the banner', async () => {
+		// Given Borja is offline with 2 pending items in the queue
+		// When context.setOffline(false)
+		// Then within 5s: the banner disappears, both items exist on the server
+		//      (verified via a second authenticated context that re-fetches the list),
+		//      and pending_ops is empty (checked via a page.evaluate reading IDB).
+	});
+});

apps/web/tests/e2e/realtime.test.ts

@@ -0,0 +1,23 @@
+/**
+ * R-E2E series — Fase 2b.1 (dual-browser-context Realtime)
+ *
+ * Exercises the end-to-end Realtime sync path through the actual SvelteKit app.
+ * Skipped until the app wires up the Realtime subscription in `/lists/[id]`.
+ */
+import { test } from '@playwright/test';
+
+test.describe.skip('Realtime sync between two user sessions (pending UI)', () => {
+	test('R-E-01: Ana adds an item → Borja sees it without refreshing', async () => {
+		// Given two browser contexts: Ana and Borja, both on /lists/[id]
+		// When Ana adds "Milk" via her sticky-form
+		// Then Borja's item list shows "Milk" within 2s (no page reload)
+	});
+
+	test('R-E-02: Presence avatar — Borja sees Ana\'s avatar when she joins', async () => {
+		// Given Borja is on /lists/[id]/session
+		// When Ana opens the same list in her own browser
+		// Then Borja's presence indicator shows Ana's avatar
+		// When Ana leaves
+		// Then Ana's avatar disappears from Borja's indicator within 3s
+	});
+});

apps/web/tests/e2e/session.test.ts

@@ -0,0 +1,28 @@
+/**
+ * S-series (Modo Compra) — Fase 2b.3
+ *
+ * These tests describe the shopping-session UX contract for `/lists/[id]/session`.
+ * Skipped until the route exists. Unskip one by one as the UI is implemented.
+ */
+import { test } from '@playwright/test';
+
+test.describe.skip('Shopping session — full-screen mode (pending UI)', () => {
+	test('S-01: /lists/[id]/session renders full-screen with no sidebar', async () => {
+		// Given Borja is logged in and on the seed list
+		// When he enters /lists/[id]/session
+		// Then the app sidebar is hidden and the layout fills the viewport
+	});
+
+	test('S-02: checking an item slides it into the CHECKED section with animation', async () => {
+		// Given at least one unchecked item
+		// When Borja taps its checkbox
+		// Then the item appears in the CHECKED section and is no longer in TO BUY
+		//      (a `flip` animation is used but we only verify final state)
+	});
+
+	test('S-03: "Finish shopping" confirms → list.status = completed → redirect to /lists', async () => {
+		// Given a list in session with some items checked
+		// When Borja taps "Finish shopping" and confirms
+		// Then the URL returns to /lists and the list card shows the "completed" badge
+	});
+});