feat: harden content integrity and contributor runway

[4444J99]

Summary

• harden content integrity by normalizing word_count/reading_time and regenerating data indices
• enforce strict Jekyll validation in CI and tighten PR acceptance checklist
• add contributor-runway documentation plus first-contribution and stranger-test intake templates
• retain additive Conductor integration notes in CLAUDE/GEMINI docs

Validation

• bundle exec jekyll build --strict_front_matter --future
• validator + indexer refresh complete with zero validation errors