Fix YAML syntax error in 2026 NYU Shanghai speakers.yml causing Jekyll build failure

[Copilot]

Jekyll builds were failing due to a Psych::SyntaxError in _data/2026/nyu-shanghai/speakers.yml — a bare - was used as the website value, which YAML interprets as an invalid block sequence entry.

# Broken — triggers: "block sequence entries are not allowed in this context at line 4 column 12"
- name: "Yang Chen"
  website: -

# Fixed
- name: "Yang Chen"
  website: https://chenyang03.wordpress.com/

All 2026 YAML data files validated against Ruby's Psych parser (same as Jekyll) — no other syntax issues found.

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