export json uses Go field names instead of schema JSON keys

[hypotyposis]

Summary

ktext export json currently emits Go struct field names for nested objects instead of schema-shaped JSON keys.

Reproduction

From the repo root:

go run ./cmd/ktext export json -file CONTEXT.yaml

Actual behavior

The JSON output contains nested keys like:

• identity.Name
• identity.URL
• constraints[].Content

Expected behavior

The JSON export should follow the documented CONTEXT.yaml schema shape, e.g.:

• identity.name
• identity.url
• constraints[].content

Likely cause

internal/export/json.go marshals schema.Context directly, but many nested structs in internal/schema/context.go only define yaml tags and not matching json tags.

Impact

This breaks machine consumers of ktext export json and makes the JSON export inconsistent with the schema/docs.