Add STAC catalog validation script and integrate into build

[samn]

Summary

This PR adds automated validation of STAC (SpatioTemporal Asset Catalog) JSON files to the build pipeline. A new bash script validates all generated STAC files using the gostac-validator tool, ensuring catalog integrity before deployment.

Key Changes

• New validation script (scripts/validate-stac.sh):

  • Automatically builds gostac-validator from source if not already present
  • Discovers and validates all STAC JSON files in the docs/stac directory
  • Provides clear pass/fail output for each file with detailed error messages
  • Exits with failure status if any files are invalid

• Updated build pipeline (package.json):

  • Integrated STAC validation into the build script to run after Eleventy compilation
  • Added new validate:stac npm script for standalone validation runs
  • Ensures STAC catalogs are valid before the build completes

Implementation Details

• The validator is cached in .cache/gostac-validator to avoid rebuilding on every run
• Uses shallow clone (--depth 1) for faster validator setup
• Provides user-friendly output with checkmarks (✓) for valid files and crosses (✗) for invalid ones
• Includes helpful error message if STAC output directory doesn't exist, guiding users to run build first
• Gracefully handles validator output parsing to detect validation results

https://claude.ai/code/session_01HqPu7U8YpWHFqhJJRAMUtq