feat(ui): marketplace recent-used chips — localStorage top-5 dedup, click to reuse, clear button (v1.20 D)

[argszero]

Summary

Item D of rant 2026-08-17T20:46:57 (UI/UE 第五轮多角度深化, v1.20): 市场「最近使用」 — recently-used model chips on the Marketplace.

• New 「最近使用」row (#mk-recent) under the marketplace toolbar (above the table): label + .chips container + 清空 button; hidden when empty
• localStorage atp-recent-models: JSON array of model ids, max 5, deduped with most-recent-first (markRecentUsed → filter out existing, unshift to front, truncate to 5; getRecentIds try/catch for corrupt/legacy data)
• Chips reuse the existing .chip pill style (model name + title with provider; hover accent highlight); renderRecent() skips ids no longer in D.MARKET
• Click a chip → directly opens that model's chat (reuses openChat — same primary action as the "使用 / 消费" button; guests get the "请先登录" toast)
• 清空 button wipes storage and hides the row
• Restore on entering the marketplace (renderMarketplace() → renderRecent()), plus immediate refresh right after a use (openChat → markRecentUsed + renderRecent)

Rant reference (verbatim)

D. 市场「最近使用」— localStorage 最近 5 个去重 chips（复用 .chip），点击直接使用

Verification

• DOM-stub smoke test: 21/21 assertions (initial hidden → use records id → dedup+cap-5 → reuse moves to front → reload restore via guest-marketplace entry → chip click opens chat + reorders → clear hides row → HTML/CSS structure)
• node --check ui/js/app.js ✓, CSS braces balanced ✓
• cargo test ✓ (1 passed), cargo fmt --check ✓
• Docs: docs/user-stories.md v1.20 entry (C marked feat(ui): table density toggle — comfortable/compact radio, localStorage, site-wide .density-compact (v1.20 C) #66, D added), ui/README.md「市场最近使用约定」section

Progress on rant 20:46:57: A (#63) + B (#65) + C (#66) + D (#67) merged; remaining E–G.