Remove @apidevtools/json-schema-ref-parser from cli-kit (inline internal $ref resolver)

[amcaplan]

What Changed

• Removed @apidevtools/json-schema-ref-parser dependency from @shopify/cli-kit package.json
• Implemented inline internal-only JSON pointer reference resolver in src/public/node/json-schema.ts
• Updated pnpm-lock.yaml to reflect dependency removal

Why

Reduce Dependabot churn: This dependency generated 13 bumps in 24 months from the dependency-removal initiative. Removing it eliminates unnecessary maintenance overhead while preserving functionality.

Replacement Details

Implemented a custom internal-only $ref resolver with cycle safety:

• Internal refs (#/... JSON pointers): Fully dereferenced inline with memoization to handle cycles
• Non-internal refs: Preserved unchanged as $ref properties to maintain prior external: false behavior
• The resolver uses a visited set to detect cycles and a resolved nodes map for memoization

Validation Results

All targeted validations pass:

• ✅ Type check: pnpm --filter @shopify/cli-kit type-check
• ✅ Linting: pnpm --filter @shopify/cli-kit lint
• ✅ Tests: pnpm --filter @shopify/cli-kit exec vitest run src/public/node/json-schema.test.ts — 16 passed

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🤖 Automated dependency-removal initiative — AI-generated draft, needs human review.