perf(e2e): skip redundant beforeAll onboard when TEST_SUITE=full

[cjagwani]

Problem

When TEST_SUITE=full, the beforeAll in brev-e2e.test.js spends ~6 min (358s) running nemoclaw onboard to create a sandbox. The full test suite (test-full-e2e.sh) then immediately destroys that sandbox in Phase 0 and runs install.sh --non-interactive which creates its own from scratch.

This is ~6 min of wasted compute on every full E2E run.

Evidence

From run 23957694836:

[408s] Starting nemoclaw onboard in background...
[358s] Sandbox e2e-test is Ready!          ← 6 min spent building sandbox
[799s] beforeAll complete

=== Phase 0: Pre-cleanup ===
  Deleting sandbox 'e2e-test'...           ← immediately destroyed
  ✓ Sandbox 'e2e-test' destroyed

=== Phase 2: Install nemoclaw ===
  ...install.sh --non-interactive...       ← builds a new one from scratch

Total run: 1121s (18.7 min). The beforeAll onboard accounts for 358s (32%) of that time.

Proposed Fix

Skip the beforeAll onboard when TEST_SUITE=full. Other suites (credential-sanitization, telegram-injection, all) still need it and are unaffected.

Expected impact

Metric	Before	After
TEST_SUITE=full duration	~18.7 min	~13-14 min
Other suites	unchanged	unchanged

Side effect (improvement)

The full test currently runs in a "resume after interrupted onboard" state (logs show [resume] Skipping preflight (cached)). After the fix, it tests a true clean install — more realistic and more valuable.