test(e2e): split + expand agent-scenarios into Phase A (22 → 47 tests)
- phase-a-structure.test.ts (156 lines, 14 tests): structural integrity,
settings panel, sidebar gear, accent colors, project name/icon, grid layout
- phase-a-agent.test.ts (210 lines, 14 tests): agent pane, prompts,
provider badge, cost display, context meter, status transitions
- phase-a-navigation.test.ts (297 lines, 19 tests): terminal tabs,
command palette, focus switching, palette categories, shortcut hints
- Original agent-scenarios.test.ts (429 lines) deleted
- 25 new exhaustive tests added