--mashlib should auto-enable --conneg #22

Problem

When using --mashlib or --mashlib-cdn, .ttl files (like Settings/Preferences.ttl) are stored internally as JSON-LD but mashlib expects them to be served as Turtle format.

Without explicitly adding --conneg, the raw JSON-LD is served with a .ttl extension, causing mashlib to fail with parse errors:

Strange: Error parse_error trying to read your preference file.
Fetcher: Error trying to parse <http://localhost:3000/melvin/Settings/Preferences.ttl> as Notation3:
SyntaxError: Line 5: Bad syntax: expected '.' or '}' or ']' at end of statement

Expected behavior

When --mashlib or --mashlib-cdn is enabled, content negotiation should be automatically enabled so .ttl files are converted from JSON-LD to Turtle on the fly.

Proposed fix

In src/config.js or bin/jss.js, automatically set conneg: true when mashlib is enabled:

if (config.mashlib || config.mashlibCdn) {
  config.conneg = true;
}

Workaround

Explicitly add --conneg when starting the server:

jss start --mashlib-cdn --idp --conneg