[Task]: Update to TypeScript v7

[Lightning00Blade]

Task to do:

We will need to install the old v6 API in tandem with the new v7 tsc to support all our linters and tooling.

[alebgl77]

Some groundwork on this, in case it is useful before someone picks it up. Checked today against main at 8f25f69.

typescript@7 is out of preview. npm view typescript dist-tags now gives latest: 7.0.2, with rc: 7.0.1-rc and next: 7.1.0-dev.20260819.1. @typescript/native-preview is still on 7.0.0-dev.20260707.2, so the published typescript package is now ahead of the preview channel.

The compiler options in this repo are already v7-clean. I installed typescript@7.0.2 in an isolated directory and ran it against the exact compilerOptions block from tsconfig.json (target: es2023, the full lib list including ESNext.Disposable, moduleResolution: bundler, allowJs, useUnknownInCatchVariables, noImplicitOverride, noFallthroughCasesInSwitch) on a probe exercising readonly arrays and a using declaration. Exit code 0, no diagnostics. So the configuration itself is not what blocks the move.

typescript-eslint is the blocker, and it is a hard one. The latest release, 8.67.0, still declares:

peerDependencies: { typescript: '>=4.8.4 <6.1.0' }

Installing v7 into this repo reproduces it directly:

npm warn While resolving: chrome-devtools-mcp@1.7.0
npm warn Found: typescript@6.0.3
npm warn   peer typescript@">=4.8.4 <6.1.0" from @typescript-eslint/eslint-plugin@8.66.0
npm warn Could not resolve dependency:

That is exactly the tandem install this issue anticipates. A workable shape is to keep the linter on a v6 install under an alias and point only the compile scripts at v7:

"devDependencies": {
  "typescript": "^7.0.2",
  "typescript-6": "npm:typescript@^6.0.3"
}

with @typescript-eslint resolved against typescript-6, and build / typecheck left on the v7 binary. The npm overrides field can pin the resolution the linter sees.

One scope note. typecheck is not limited to src/ and tests/. tsconfig.json pulls in roughly sixty third_party/devtools-frontend/front_end/** paths plus a files entry on front_end/third_party/acorn/package/dist/acorn.mjs. So the migration is gated on v7 also compiling that slice of the submodule, not just this repo's own sources. I did not fetch the submodule, so I have not tested that half and cannot speak to it.

Happy to open a PR for the dual install if that shape matches what you have in mind, or to leave it with you if this is already in flight.