Feat/instance accessor syntax paths

[kervel]

an attempt to make paths in diff/patch algo compliant with the https://linkml.io/linkml-model/latest/docs/specification/02instances/ doc

Examples

• Diff example (identifier-based):
  • Change: diagnosis.name in the first medical event of P:002
  • New delta path: ["objects","P:002","has_medical_history","0","diagnosis","name"]
• Patch example (identifier-based add):
  • Path: ["objects","P:003"] with a new Person object as “new” value (allowed when selector does not match an existing element; behavior appends).
• Turtle/Mapping (unchanged for paths):
  • Mapping keys remain addressed by key names (e.g., ["things","alpha"]).

[kervel]