Migrate AI Agent Run form tab bar to mj-tab-nav

The AI Agent Run form (`packages/Angular/Explorer/core-entity-forms/src/lib/custom/ai-agent-run/ai-agent-run.component.html`) hand-rolls its tab bar (`.tabs` / `.tab` buttons with `activeTab` + `changeTab()`), predating the canonical `mj-tab-nav` component in `@memberjunction/ng-ui-components`.

Per the design-system convention ("spot a hand-rolled primitive: file the two-step issue, don't expand your PR"), the branchable-agent-runs work (PR #3296) added its Branches tab following the existing local pattern rather than migrating the bar in-PR.

Two-step migration:
1. Confirm `mj-tab-nav` covers the form's needs (5 tabs, icons, lazy-load gating stays in the host).
2. Migrate the tab bar markup + styles, preserving `changeTab()` lazy-load side effects (`visualizationLoaded` / `analyticsLoaded` / `branchesLoaded`).

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

Start with packages/Angular/Explorer/core-entity-forms/src/lib/custom/ai-agent-run/ai-agent-run.component.html and inspect the canonical mj-tab-nav in @memberjunction/ng-ui-components. Confirm it supports the five tabs and icons, then migrate the tab markup and styles while keeping lazy loading in changeTab(). Done means visualizationLoaded, analyticsLoaded, and branchesLoaded still update correctly.

Written by the indexing model from the issue text.