Explore page redesign: browsable, composable query experience

[harshach]

Goal

Make the Explore page truly browsable: the browse-tree location and the quick filters should compose into one visible query instead of clearing each other.

Problems with the current Explore page

• Clicking a tree location replaces the active quick filters (and vice versa) — browsing and filtering fight each other.
• No persistent representation of the active query; filters are hard to discover and remove.
• Filter dropdowns require an extra Update click, show raw entityType keys (e.g. tablecolumn), and self-filter their own options (selecting Column hides every other type).
• Selecting an asset type still allows browsing into services that cannot contain it (a Table only lives under Database services).
• Result cards are oversized (3 per viewport) with wrapping breadcrumbs and a heavy blue selected state.

Proposed experience

• browsePath (tree location) ANDs with quickFilter (facets); both render in a persistent QUERY bar as removable chips ("In Databases / Service redshift prod / Type Table"), with hierarchical removal and Clear.
• Immediate-apply facet dropdowns with human-readable labels, own-field-excluded options, and compact design styling.
• Incompatible categories gray out and collapse; per-level counts; tree highlight follows the chips.
• Compact white result cards with single-line middle-ellipsized breadcrumbs and a stroke icon set.

Implemented by PR #28892.