feat(modules): agentic 404 to answer agents

[larbish]

Summary

Answer agent 404s with a markdown document listing the site's machine-readable entry points, instead of JSON error body. Comes from an Is Agentic scan of docus.dev, which flagged the JSON 404 as a dead end for crawlers.

# 404 — Page not found

`/wrongpath` was not found on this site.

## Where to look next

- [/llms.txt](/llms.txt): index of Docus
- [/llms-full.txt](/llms-full.txt): the full content of this site as a single markdown document
- [/sitemap.xml](/sitemap.xml): every page, with its last modification date
- [/.well-known/skills/index.json](/.well-known/skills/index.json): agent skills published by this site
- [/](/): home page

Changes

New module (layer/modules/not-found/)

Prepends a Nitro error handler that only answers page-ish 404s.

Browsers (text/html), API clients (application/json, /api/**, *.json), $fetch (sec-fetch-mode: cors) and assets keep the default error body. Response keeps its 404 status, plus Vary: Accept so CDNs don't mix the variants.

Links are resolved at build time so the document never points at a route the site doesn't serve: /llms-full.txt only when enabled, /.well-known/skills/index.json only when skills exist.

Opt out with docus.notFound: false.

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Project	Deployment	Actions	Updated (UTC)
docus	Ready	Preview	Aug 25, 2026 5:21pm

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commit: 7de71f4