Move from JS to TS

[aryanjasala]

Convert build sources to TypeScript

Context

Our block theme and feature-plugin skeletons are authored in JavaScript. We want them to be TypeScript-first so consuming projects get type safety, editor IntelliSense, and earlier error detection. @wordpress/scripts already supports TypeScript, so this is a build-time change only — runtime behavior and shipped assets stay the same.

Goal

All source under src/ is written in TypeScript (.ts/.tsx), type-checked in CI, with no change to compiled output or runtime behavior.

Scope

• Block theme
• Feature-plugin skeleton

(Both should end up with an identical TypeScript + lint setup.)

Deliverables

• TypeScript tooling configured (tsconfig, ambient type declarations, a type-check script).
• All src/ JavaScript converted to .ts/.tsx, including blocks and components.
• Linting and type-checking run in CI for TypeScript on every relevant PR.

Definition of done

• Type-checking passes across src/ with a reasonably strict config.
• JS/TS linting and CSS linting pass.
• build and start work unchanged; compiled JS output is equivalent to before.
• No JavaScript remains under src/ (root build-config files may stay JS).

Considerations

• Use first-party @wordpress types where available; fall back to community type stubs only where a package ships none.
• Keep the runtime React version and its type definitions aligned to avoid duplicate/incompatible React types.
• Type-checking is additive — it must not alter the built assets or block registration.