docs: remove generic LLM boilerplate ai_passage.md (#31)

ai_passage.md was a 53-line, ~1000-word essay on the history and
ethics of AI in general — entirely unrelated to the hawk project,
no README/AGENTS.md/CHANGELOG.md reference to it. It looks like
LLM-generated filler committed in '99261ca Fix CI formatting and
toolchain hygiene' to satisfy a 'must have an essay' requirement
that no longer applies. Untrack and delete.

Author: Patel230