Build with TypeScript 7 once 7.1 ships the programmatic API

[domoritz]

Follow-up to #9923, which moved tsc typechecking to the native TypeScript 7 compiler. The rollup build still runs TypeScript 6, because TS 7.0 ships the native compiler without a programmatic API and @rollup/plugin-typescript needs that API. typescript is therefore aliased to @typescript/typescript6, which the plugin (and typescript-eslint) consume.

Trigger

TypeScript 7.1 shipping the programmatic API, and @rollup/plugin-typescript supporting it. The concrete signal to watch is the plugin declaring a typescript peer range that admits 7.x (it is currently >=3.7.0, which accepts 7 by version number but not in practice, since 7.0 has no API to call).

Expected change

Ideally just a dependency bump:

• @rollup/plugin-typescript → a version supporting TS 7
• drop the typescript → @typescript/typescript6 alias and the @typescript/native alias, going back to a plain typescript dependency — only if typescript-eslint also supports 7.x by then; otherwise the alias has to stay for eslint even once the build is migrated

Motivation (measured on #9923's branch)

	TS 6	TS 7 native
emit 748 files (.js + .d.ts + maps)	2.25 s	0.47 s
tsc --noEmit typecheck (837 files)	2.86 s	0.58 s

rollup.config.js has two builds, each with its own typescript() plugin instance on the same src/index.ts input, so TypeScript compiles twice — roughly 4.5 s of the ~7.3 s build. A native build should land around ~3.5 s.

Things to check beyond bumping the dep

• Do not split into a separate tsc emit + rollup bundle step. This was considered and deliberately rejected. Chained sourcemaps (tsc → rollup, with both sourceMap and declarationMap) are easy to get subtly wrong, and it is the main reason to wait for the plugin rather than restructure the pipeline.
• npm run watch (rollup -c -w) must keep working. A separate tsc emit step would not integrate with rollup's watch loop, which is the other reason to keep the plugin driving emit rather than doing it ourselves.
• Expect .d.ts churn. TS 7 emits single quotes for string literal types — export declare const ROW: 'row' where TS 6 emits "row". Measured: 38 of 187 .d.ts files affected, plus every .d.ts.map. Semantically identical, but it is published output, so decide consciously whether to accept it.
• Byte-compare the build output. Clean build before and after, comparing all 378 files in build/ (bundle, minified bundle, .d.ts, .map). chore(deps): typecheck with TypeScript 7 #9923 did exactly this to prove the alias arrangement changed nothing; the same check should gate this change, with the .d.ts quote-style diff as the only expected delta.
• Confirm bin/vl2vg and friends still work against the rebuilt bundle (the CLI job covers this).

Related

• chore(deps): typecheck with TypeScript 7 #9923 — typecheck with TypeScript 7 (the alias arrangement, and why the build was left on 6)
• chore: generate schema with ts-json-schema-generator v3 (native TypeScript 7) #9921 — schema generation moved to ts-json-schema-generator v3 native
• chore(deps): upgrade to TypeScript 7 vega#4324 — the equivalent TypeScript 7 move in vega