feat: llms.txt/llms-full.txt route handlers

[ceIia]

this is a follow up to #191.

changes:

• remove build time llms.txt and llms-full.txt generation in favor of route handlers. we make them fully static, and let Vercel handle CDN level caching on future deployments, that way we don't risk machines/browsers caching a stale version for too long (and we don't explode Rocicorp's Vercel bill).
• properly have the .md suffix to documentation links inside llms.txt, llms-full.txt, and the markdown files themselves.
• fix a bug where some links would be missing a space between the closing parenthesis and the word after
• update the /docs/llms page

notes:

1. i held off from adding the "Copy page" or "View as Markdown" buttons that most other doc sites/frameworks have been adding, but if you think it would be useful, let me know.
2. @aboodman you mentionned a "few follow-up things I think we should do" in the other PR, let me know what you had in mind - it's fun working on a more "artisanal" docs site!

[vercel]

@ceIia is attempting to deploy a commit to the Rocicorp Team on Vercel.

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[0xcadams]

Can you explain what this PR is about? Sorry it got missed. Why can't we keep the build time

[aboodman]

I think @ceIia was probably feeling it was awkward/weird to generate /doc/foo-page.md statically for every single page. I have similar feeling. I prefer it being runtime generated too , for consistency with how rest of docs work.

[aboodman]

Sorry for forgetting to review this @ceIia - I really appreciate the contribution.

it's fun working on a more "artisanal" docs site!

😂