Model at the repo root + laya_browser.py: load with LayaBrowser.from_pretrained('cklxx/laya-browser') or serve a TypeSafe endpoint

v19s: WebChain real-site trajectories, format v5, webgym x7 + DAgger, harness fixes; replaces v17s

Single model: v17s (suite A 85 %, suite B 100 %, webgym 47 %); replaces v15s (kept in history)

Single model: v15s (clean retrain, suite B 100 %); remove v10, v10s, v11s, v14s (kept in history)

code: uv project (pyproject + uv.lock), verify.py, sample_request.json, fast-path import fix