docs: align spec yaml ai_context shape

[CooperSheroy]

Summary

• update core-spec/spec.yaml so ai_context is shown as a structured object while noting simple strings are also accepted
• add the relationship ai_context field that already exists in the JSON schema and spec docs

Closes #141.

Validation

• ruby -e 'require "yaml"; YAML.load_stream(File.read("core-spec/spec.yaml")); puts "YAML parse OK"'
• jq empty core-spec/osi-schema.json

[jbonofre]

LGTM.

@khush-bhatia @QMalcolm as it's a spec change, can you please do a pass? Thanks!

[khush-bhatia]

This change is making the yaml version of the spec strictly only allow three subfields which are instructions, synonyms and examples.

Instead we shoudl change the type here to be {} so it can support arbitrary key values .

The issue #141 also suggests the same thing. See

# Optional: Additional context for AI tools.
# Can be either:
#   - A free-form string, or
#   - A structured object with optional keys:
#       instructions: string  # how AI should use this entity
#       synonyms:     []      # alternative names / terms
#       examples:     []      # sample questions or use cases
#     (additionalProperties: true — vendors may add more keys)
ai_context: {}  # see AIContext in osi-schema.json

[jbonofre]

Good point. Agree!