ci: enforce registry artifact drift check in code-check workflow

[Yeom-JinHo]

Description

This PR adds a CI guard for registry artifact drift in the code-check workflow.
CI now rebuilds registry artifacts and fails when generated files are not committed.

Changes

• Added a registry-drift job to .github/workflows/code-check.yml.
• Unified execution with local workflow by using pnpm build:registry in CI.
• Validated generated artifact paths (registry.json, __index__.tsx, public/r, llms files).
• Improved failure output to show changed files and the exact fix command.

Motivation

Generated registry outputs can drift from source changes and still pass lint/type checks.
This job catches that early and keeps local and CI behavior consistent.

Breaking Changes

None.

Screenshots

N/A (CI/workflow-only change).

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