Fix ambiguous Skills heading lookup in packed-release e2e

[ScriptedAlchemy]

packages/workbench/tests/packed-release.e2e.test.ts can flake because getByRole('heading', { name: 'Skills' }) also matches the Source skills h2.

Narrow the locator to the intended heading (for example, exact name or level) with #600 PR 2/3.

[ScriptedAlchemy]

Duplicate of #632 (same getByRole('heading', { name: 'Skills' }) / Source skills strict-mode ambiguity; #632 carries the note that #629 already removed the locator, so the ask is on the rebuilt shell's acceptance tests). Tracking there.