feat(WebUI Smoke CLI): expand smoke coverage (App launcher P1, model serving, RBAC basics)

## Parent

- Epic: [FR-2871](https://lablup.atlassian.net/browse/FR-2871)
- Spec Task: [FR-2872](https://lablup.atlassian.net/browse/FR-2872)
- Spec: `.specs/FR-2871-webui-smoke-cli/spec.md` § FR-J

## Goal

Expand the `@smoke` catalog beyond the FR-A starter set. **App launcher is priority 1** because the wsproxy / app-proxy path is the most frequent failure mode at customer sites. Also adds basic model-serving and single-account-safe RBAC checks.

## Acceptance criteria

- [ ] **App launcher (P1)** — start a session, launch one app (jupyter or terminal), confirm the app page actually opens through the app-proxy. This is the most frequent failure mode at customer sites.
- [ ] Model serving — basic serving endpoint deploy + invocation.
- [ ] Basic RBAC — single-account-safe permission checks (no cross-user assertions).
- [ ] App launcher smoke fails loudly when wsproxy / app-proxy is misconfigured (distinguish "session never reached RUNNING" from "session running, app proxy 502").

## In scope

- `e2e/tests/smoke/app-launcher.spec.ts` (new)
- `e2e/tests/smoke/model-serving.spec.ts` (new)
- `e2e/tests/smoke/rbac-basics.spec.ts` (new)
- Tag annotations following FR-A taxonomy

## Out of scope

- Cross-user RBAC scenarios (excluded from `@smoke` by convention)
- Visual regression

## Test plan

- Run `--include @smoke` against staging with a session-launch-capable account; confirm app launcher case passes and produces a distinct failure reason when app-proxy is forced offline.
- Verify model-serving case end-to-end against staging.

## Dependencies

- Hard: FR-C (runner must be in place)
- Soft: FR-F (single-account-safe utils are nice-to-have; without them this task may need to duplicate small helpers locally)

JIRA Issue: FR-2884

[FR-2871]: https://lablup.atlassian.net/browse/FR-2871?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
[FR-2872]: https://lablup.atlassian.net/browse/FR-2872?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ