Remove fragile publication snapshot tests

[mnarayan]

Summary

• remove tests that lock exact README headings, contributor terminology, title, URLs, and clone commands
• retain behavioral checks for placeholder validation, metadata/disclosure workflows, publishing, themes, AI disclosure, CRediT, and licensing
• change no publication content or theme files

Verification

• 40 tests passed
• Ruff check and format check passed
• diff contains test files only