/explore offers a Forges chip beside All, Apps and People #6040

Intent: every kind the explorer ranks is one tap away.

Seen: /explore's kind chips are All, Apps and People, while its query (and llms.txt) also takes kind:forge.

Done:

• [ ] /explore draws a "Forges" chip linking /explore?q=kind%3Aforge, marked aria-current when that is the query
• [ ] the chip keeps the current sort, as the other kind chips do
• [ ] a test: the chip is drawn, and is current on ?q=kind:forge

Files: src/web/studio/explore.ts, its test. Risk: design-lint; use the chips' existing class.