Support #this fragment for LongChat spec compliance #28

Summary

The Solid LongChat spec identifies the chat resource as #this within a document. Currently, solid-chat has partial support but the date navigation breaks when URLs contain fragments.

Background

Spec-compliant LongChat structure:

{
  "@id": "#this",
  "@type": "meeting:LongChat",
  "meeting:message": [...]
}

Where:

• Document (chat.json) = the file
• chat.json#this = the chat resource
• Messages hang off #this

Current State

Works:

• Title lookup (line 1885) already handles #this:

  const chatNode = subject.uri.includes('#') ? subject : $rdf.sym(subject.uri + '#this')

• Message extraction queries all content in doc regardless of subject

Broken:

• Date navigation regex expects URL to END with chat.json:

  const DATE_SHARD_PATTERN = /\/(\d{4})\/(\d{2})\/(\d{2})\/chat\.(json|jsonld|ttl)$/

• chat.json#this won't match (has fragment after filename)

Proposed Fix

Update regex to allow optional fragment:

const DATE_SHARD_PATTERN = /\/(\d{4})\/(\d{2})\/(\d{2})\/chat\.(json|jsonld|ttl)(#.*)?$/

This is a 1-line change.

Benefits

• Full spec compliance with Solid LongChat
• Enables future prev/next links at RDF level on #this
• Works with both chat.json and chat.json#this URLs