Bring the root README up to date

[dcellison]

Summary

This pull request checks the root README against the live site, current catalogues, canon, CI, and the repository licence.

• Point the shelf and explorer links at the working HTTPS custom domain, phi.syrinx.net, while describing only the reader-facing shelves as rendered output.
• Describe the Short Road and pamphlet shelf at their actual scope, and add the translation certification mark and current near-term plan to the repository map.
• Replace the claim that machines validate everything with the separate lexical, sentence, and translation gates that the repository actually runs.
• Bring the licensing summary into line with LICENSE, including the Solarpunk exception and third-party fonts.

The Humanizer and voice pass replaced a long list of validation disclaimers with one concrete boundary: machinery can reject a misplaced particle, but it cannot decide whether a translation has understood Morris.

Checks

• all 28 local README links resolve in the repository
• https://phi.syrinx.net/ returns 200
• https://phi.syrinx.net/explore.html returns 200
• python3 scripts/build_site.py
• python3 scripts/validate_examples.py
• python3 scripts/validate_sentences.py
• python3 scripts/test_sentence_validator.py
• python3 scripts/test_vocabulary_schema.py
• python3 scripts/content_vocabulary_decisions.py --check
• python3 scripts/test_content_vocabulary_decisions.py
• python3 scripts/test_name_forms.py
• python3 scripts/test_translation_layers.py
• python3 scripts/translation_process_status.py --check
• python3 scripts/test_translation_process_status.py
• phonetic-neighbour baseline comparison
• generated-reference synchronization
• git diff --cached --check