see issue #40

Summary

Add longchat-specific SHACL shapes to shapes/chat.ttl without changing the existing published chat shapes.

What Changed

• added LongChatChannelShape for mee:LongChat channels
• added LongChatMessageShape for signed chat messages with append-only replacement links
• added AppendOnlyMessageVersionShape for message version chains via dct:isReplacedBy
• added DeletedLongChatMessageShape for replacement messages carrying deletion timestamps
• added LongChatThreadShape for sioc:Thread reply structures
• added LongChatActionShape for sentiment/action nodes targeting chat messages
• accepted both https://schema.org/ and legacy http://schema.org/ predicates for compatibility with existing data
• documented that sec:proofValue currently signs the core message fields only

Why

The current SolidOS long chat implementation stores richer chat data than the legacy chat shapes describe:

• dated message documents (YYYY/MM/DD/chat.ttl)
• signed messages
• append-only edit and delete flows
• thread membership through sioc:Thread
• historical use of http://schema.org/ in deployed chat data

These additions model that behavior as new semantic variants inside the existing chat domain, while preserving the existing Chat* shapes unchanged.

Compatibility

• no existing Chat* shape was renamed or modified incompatibly
• legacy http://schema.org/ data remains valid
• newer https://schema.org/ data is also accepted

Validation

Validated successfully with:

• python3 scripts/validate-shacl-shapes-file.py shapes/chat.ttl
• python3 scripts/check-namespaces-and-names-file.py shapes/chat.ttl
• python3 scripts/check-metadata-and-immutability-file.py shapes/chat.ttl