Add llms.txt for LLM-optimized doc discovery

[ScavieFae]

Summary

• Adds public/llms.txt following the llmstxt.org spec — Ink currently returns 404 at /llms.txt
• Covers all ~43 live doc pages, organized by developer workflow rather than sidebar order
• RPC endpoints and chain IDs inlined as plaintext for zero-click access by coding assistants
• Uses the spec's ## Optional section to deprioritize non-essential pages (FAQ, Community, Brand Kit)

Why

Developers increasingly use AI coding assistants (Cursor, Claude Code, Copilot) to scaffold projects. When someone asks "help me deploy a contract on Ink," the assistant has no structured entry point to Ink's docs — it either hallucinates outdated info or falls back to generic OP Stack docs.

Both Base and Optimism already serve llms.txt. Ink is the only major Superchain network without one.

Design choices

• Sectioned single file — right for Ink's current doc size (~45 pages). More structured than Optimism's flat dump; doesn't need Base's sub-file architecture yet.
• Enriched descriptions — each link carries enough context for an LLM to decide whether to follow it (e.g., Pre-installed Contracts lists Safe, Multicall3, Permit2, ERC-4337 EntryPoints, etc.)
• RPC duplicated intentionally — once in the Tools section, once as inline quick reference. This is the feat: init #1 thing coding assistants need.
• Excluded: Ink Kit (archived), Kraken Verify (404s at /build/kraken-verify)

Suggested follow-up

Serve .md versions of high-traffic pages (Getting Started, Onchain Clients, deployment tutorials, contract address tables). The spec supports this as page-url.md — low-effort on Nextra since the source is already Markdown.

Test plan

• Verify llms.txt is served at docs.inkonchain.com/llms.txt after deploy
• Spot-check that all URLs in the file resolve (validated as of March 2026)