Add v4 Related Approaches doctrine pages

[ThorFuchs]

Summary

• Adds the Program/About Related Approaches hub plus all 10 child comparison pages.
• Wires the new surface into Program/About navigation and cross-links from Discover, Program, Agenda/KMR, Corpus, Media, and Review Kit.
• Keeps existing KMR Related Approaches routes live as specialist no-externalities comparison surfaces.
• Adds a focused v4 Related Approaches assertion and updates the footer assertion to the current v4 core-lane set.

Validation

• PATH="/opt/homebrew/opt/ruby@3.3/bin:$PATH" bundle exec jekyll build --baseurl ""
• npm exec -- pagefind --site _site --output-subdir pagefind
• .github/scripts/smoke-test.sh _site
• PATH="/opt/homebrew/opt/ruby@3.3/bin:$PATH" .github/scripts/link-check.sh _site
• npm run headers:test
• npm run headers:dry-run (dry-run completed; sandbox blocked only Wrangler log-file write under ~/Library/Preferences)
• python3 scripts/assert_v4_related_approaches.py _site
• Existing v4, manifest, footer, Results, World Readout, preflight, and scientific plate assertions
• Playwright desktop/mobile screenshot pass for hub, representative child pages, and cross-linked routes
• git diff --check

Notes

• Website-only change; no corpus, taulib, atlas, data export, item-count, or top-nav changes.
• A separate optional Problem Ledger enrichment assertion still reports pre-existing source-entry-record mismatches and is not part of this release scope.