docs: publish llms.txt and llms-full.txt for agent-friendly ingestion (#18276)

Two machine-readable entry points to the Hermes Agent docs:

  /llms.txt         curated index of every doc page, one link per page
                    with short descriptions. ~17 KB, safe to load into
                    an LLM context window.
  /llms-full.txt    every page under website/docs/ concatenated as markdown.
                    ~1.8 MB. For one-shot ingestion by coding agents and
                    RAG pipelines.

Both files are also served from /docs/llms.txt and /docs/llms-full.txt
(Docusaurus serves website/static/ under baseUrl=/docs/). Some agents and
IDE plugins probe the classic site-root path; the deploy workflow now copies
both files to _site root so either URL works.

Conforms to the emerging llmstxt.org spec: H1 project name, blockquote
summary, short install command, GitHub link, then curated sections
mirroring the docs-site navigation (Getting Started, Using Hermes,
Features, Messaging, Integrations, Guides, Developer Guide, Reference).

Generated by website/scripts/generate-llms-txt.py. Wired into prebuild.mjs
so every 'npm run build' and 'npm run start' refreshes the files alongside
the existing skills.json extraction. Both outputs are gitignored (same
precedent as src/data/skills.json).

Descriptions in llms.txt are pulled from each page's frontmatter, so they
stay current automatically. All ~80 section slugs are validated against
the filesystem at generation time; an invalid slug would fail the prebuild.

website/docs/index.md

@@ -55,3 +55,12 @@ It's not a coding copilot tethered to an IDE or a chatbot wrapper around a singl
 - **Full web control** — Search, extract, browse, vision, image generation, TTS
 - **MCP support** — Connect to any MCP server for extended tool capabilities
 - **Research-ready** — Batch processing, trajectory export, RL training with Atropos. Built by [Nous Research](https://nousresearch.com) — the lab behind Hermes, Nomos, and Psyche models
+
+## For LLMs and coding agents
+
+Machine-readable entry points to this documentation:
+
+- **[`/llms.txt`](/llms.txt)** — curated index of every doc page with short descriptions. ~17 KB, safe to load into an LLM context.
+- **[`/llms-full.txt`](/llms-full.txt)** — every doc page concatenated into a single markdown file for one-shot ingestion. ~1.8 MB.
+
+Both files also resolve at `/docs/llms.txt` and `/docs/llms-full.txt`. Generated fresh on every deploy.