AI policy: update to forbid generative AI
As discussed at the hackathon:
- Explicitly forbid generative AI.
- Shorten the policy.
- Split the actual policy and reasoning into separate sections.
Rename to "AI policy" while at it to make clearer what this is about.
Related: https://postmarketos.org/blog/2026/02/10/fosdem-and-hackathon/#monday
Signed-off-by: Oliver Smith ollieparanoid@postmarketos.org