docs: add llms.txt to docs for AI friendly navigation

[dangrondahl]

Summary

Add auto-generated llms.txt support for Kosli documentation following the llms.txt specification. This enables LLMs to better understand and navigate the documentation structure.

Changes

• Configure Hugo to auto-generate llms.txt in plain text format
• Create dynamic template that pulls all documentation sections and pages
• Include frontmatter summaries (200 char limit) for each page
• List all 92 CLI commands in the Reference section
• Organize content with main sections and an Optional section for extended context

How it works

The llms.txt file is automatically generated during the Hugo build process:

• Main sections: Understanding Kosli, Getting Started, Tutorials, Implementation Guide, Administration, Integrations
• Reference section includes complete CLI command index and API references
• Optional section provides metadata that can be skipped for shorter context windows
• Uses frontmatter summary field for page descriptions (falls back to no description if missing)

Files changed

• docs.kosli.com/config.yaml: Added outputs and outputFormats configuration
• docs.kosli.com/layouts/index.llms.txt: New Hugo template for generating llms.txt

Testing

Build and verify the output:

make hugo-local
# Check the generated file at docs.kosli.com/public/llms.txt


## Reference
- https://docs.google.com/document/d/171uonXT-eqaqD1iYQaeEPBzQQH8wICC3c1vi-6XcSFM/edit?tab=t.0