Optimize hot-path utility helpers for string escape and object filtering

[Copilot]

Several utility helpers were doing avoidable per-call work (regex construction, linear key scans) in hot paths. This update reduces repeated work while preserving behavior.

• HTML escape/unescape fast path
  • Hoist maps and regex creation to module scope and reuse during replacements.
• Object filtering efficiency
  • Use Set membership for pick/exclude to avoid repeated linear scans.
• Behavior coverage
  • Add duplicate-key cases to validate pick/exclude semantics.

const ESCAPE_REGEX = new RegExp(`(${Object.keys(ESCAPE_MAP).join('|')})`, 'g')
return text.replaceAll(ESCAPE_REGEX, (match) => ESCAPE_MAP[match])

Original prompt

Identify and suggest improvements to slow or inefficient code

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