feat: add x-render-dependencies for SSR/SSG metadata

[SisyphusZheng]

Summary

Adds one experimental x-render-dependencies?: string[] field to CustomElement for direct custom element dependencies referenced by an element's own render output.

Consumers such as SSR and SSG tools can use the direct edges to resolve transitive dependencies, detect cycles, and prepare component definitions before rendering.

Closes #147.

Scope

This PR now follows the issue's intentionally narrow scope and adds only x-render-dependencies. Renderer selection, hydration capability, and shadow-root configuration are left for separate proposals.

The x- prefix is proposed as an experimental convention, following the discussion in #38; it is not presented as an already-established CEM extension mechanism. The field intentionally uses string[] without an incomplete ASCII-only tag-name regular expression.

Changes

• Adds x-render-dependencies to the TypeScript schema.
• Regenerates schema.json from schema.d.ts using the repository build command.
• Adds tests that assert the field is present on custom element declarations and that a positive example is accepted.
• Adds an Unreleased changelog entry.

Validation boundary

The generated JSON Schema describes the field as an array of strings, but this PR does not claim that every malformed value is currently rejected. #138 tracks the existing declaration-union / anyOf validation ambiguity. Fixing that issue is intentionally out of scope here.

Motivating implementation

OpenElement provides a working nested-component rendering path that motivates making direct render dependencies discoverable:

• packages/element/src/public-runtime.ts
• packages/element/src/internal/compiled/server/index.ts
• packages/element/__tests__/compiled-server/compiled-composition.test.ts

This is evidence for the metadata use case, not a claim that every SSR implementation uses the same algorithm.

Verification

npm run format
npm run build
npm test

The test suite passes 3/3, and running the schema build repeatedly produces the same schema.json.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.