fix(ui): fold tag filters and card tags on large projects

[piekstra]

On a project with many flows, the tag filter row listed every tag and could fill half the screen, and card tags were clipped mid-word against the "never run" label.

• The filter row shows the 12 most used tags (then by name), any selected tag, and a "N more" button that expands to all of them.
• A card shows two tags and a "+N" count; the hidden tags are in its tooltip.

Captured from a 20-flow sample project with 38 tags at 1280x720.

Before	After

Expanded:

[piekstra]

Review fixes: a selected tag that no flow has any more stays in the row so it can be cleared; the expand button has aria-expanded and the +N chip an aria-label; docs/ui.md describes the fold.