Asset browser: implement clickable breadcrumb navigation

Goal

Make the current breadcrumb trail in the asset browser clickable, allowing users to navigate up the folder hierarchy in a single click instead of repeatedly pressing the .. button.

Context / integration points

• The breadcrumb currently shows: Home / assets / characters / models (static display only).
• Each segment should become a clickable button.
• Complements #67 (closed) (tree panel) and #70 (closed) (tree-exclusive) — all are folder navigation improvements.
• Similar to breadcrumb navigation in most file browsers (VSCode, Finder, Windows Explorer).

Design

• Render each breadcrumb segment as a button (visual distinction: underline on hover or similar).
• Clicking a segment navigates to that folder and updates the main grid view.
• The home icon/first segment navigates to the root asset/ folder.
• Breadcrumb updates dynamically as the user navigates.

Tasks

• Make breadcrumb segments clickable (style as buttons with hover state)
• Connect breadcrumb clicks to folder navigation
• Update breadcrumb display as user navigates
• Ensure visual affordance (cursor: pointer, hover styling)

Acceptance criteria

• Clicking any breadcrumb segment navigates to that folder.
• The main grid updates immediately.
• Breadcrumb visually indicates interactivity (hover state).

Dependencies

Unblocked. Nice-to-have polish; does not depend on tree panel or tree-exclusive mode.

Out of scope

• Dropdown menus on breadcrumb segments (for sibling folders).
• Path validation or error handling for missing folders.