Resolving a root-level $ref destroys the "definitions" that other $refs in the same document point to

Resolving a $ref merges the referenced section into the target node with a plain per-key assignment. If the referenced section itself has a definitions key, the document's root definitions is overwritten, destroying pointer targets that other $refs in the same document still need.

Because the schema is mutated in place, the outcome depends on resolution order: a perfectly valid #/definitions/… reference becomes unresolvable.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$ref": "#/definitions/entry",
  "definitions": {
    "entry": {
      "type": "object",
      "properties": { "p": { "$ref": "#/definitions/shared" } },
      "definitions": { "unused": { "type": "null" } }
    },
    "shared": { "type": "string" }
  }
}

$ref '/definitions/shared' in 'file:///.../schema.json' can not be resolved.

Another issue, I'm not sure if it's relevant, is with the $ref path itself:

{
	"$schema": "http://json-schema.org/draft-07/schema#",
	"$ref": "#/definitions/entry",
	"definitions": {
		"entry": {
			"type": "object",
			"properties": {
				"p": {
					"$ref": "#/definitions/entry/definitions/testDef"
				}
			},
			"definitions": {
				"testDef": {
					"type": "null"
				}
			}
		}
	}
}

#/definitions/entry/definitions/testDef won't resolve, when it's technically correct
#/definitions/testDef DOES, but it's actually incorrect, as # always point to the root, and "testDef" is NOT in /definitions

Reproduces in 5.7.2, 6.0.0-next.1, 6.0.0-next.2 and 6.0.0-next.3.
It's not a regression but a long-standing behaviour.
Also reproduces in VS Code (json-language-features 10.0.0).

Start by reproducing the two JSON Schema examples against the $ref resolution entry point in the TypeScript language service. Trace how resolving a root-level reference mutates definitions and how fragment paths are interpreted. Done means root-level and nested definitions remain resolvable in resolution-order-independent regression coverage.