Add metadata to track "AI Level"

[DavidSouther]

How much AI:

• None - no AI was used.
  • Claude, ChatGPT, or other "chat" interfaces may have been used for reference, but their output was not included directly in the code.
• Some - AI was consulted while writing this section, and some words or phrases may have been copied, but the bulk was written by the human author.
  • Copilot, CodeWhisperer, inline AI, or ailly --edit may have been used for some code.
• Most - a human directed an AI to create this section. While they may have applied some editing, they have reviewed and revised it for accuracy.
  • Significant portions of code were written by an LLM, under the direction of and reviewed by a human.
  • Generating an entire file with Ailly, and then editing it.
• All - this content was created entirely by AI, and no human has reviewed it before publishing.

(The line between some and most is fuzzy- you'll know it when you do it.)

[DavidSouther]

This will go on the excerpt level.

genai: none, some, most, all. Default none if not present.