Clean up esbuilding of extensions

[mjbvz]

• Make sure we still always type check using tsgo --noEmit
• Align names of esbuild files
• Convert all esbuild files to typescript. We use the .mts extension to avoid annoying node warnings about using pacakges

[Copilot]

Pull request overview

This PR refactors extension esbuild entrypoints and shared esbuild helpers, aiming to standardize filenames, move scripts to TypeScript (.mts), and ensure extension builds are still type-checked via tsgo --noEmit.

Changes:

• Rename/realign per-extension esbuild scripts (e.g. esbuild.webview.mts, esbuild.notebook.mts) and update package.json scripts accordingly.
• Introduce shared .mts esbuild helpers (extensions/esbuild-*-common.mts) and update extensions to import them.
• Update the build pipeline to run a separate tsgo --noEmit typecheck step for esbuild-bundled extensions.

Reviewed changes

Copilot reviewed 26 out of 27 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
extensions/simple-browser/package.json	Updates build script to point at new esbuild entrypoint name.
extensions/simple-browser/esbuild.webview.mts	Switches shared helper import to .mts.
extensions/notebook-renderers/package.json	Updates notebook build script name.
extensions/notebook-renderers/esbuild.notebook.mts	Switches shared helper import to .mts.
extensions/mermaid-chat-features/package.json	Updates webview build script name.
extensions/mermaid-chat-features/esbuild.webview.mts	Switches shared helper import to .mts.
extensions/mermaid-chat-features/esbuild.mts	Switches shared helper import to .mts.
extensions/mermaid-chat-features/esbuild.browser.mts	Switches shared helper import to .mts.
extensions/media-preview/esbuild.mts	Switches shared helper import to .mts.
extensions/media-preview/esbuild.browser.mts	Switches shared helper import to .mts.
extensions/markdown-math/tsconfig.browser.json	Adds a browser tsconfig for web typechecking.
extensions/markdown-math/package.json	Updates build script to .mts.
extensions/markdown-math/esbuild.notebook.mts	Switches shared helper import to .mts and adds a typed callback param.
extensions/markdown-math/esbuild.mts	Switches shared helper import to .mts.
extensions/markdown-math/esbuild.browser.mts	Switches shared helper import to .mts.
extensions/markdown-language-features/tsconfig.browser.json	Narrows browser project inputs for web typechecking.
extensions/markdown-language-features/package.json	Reworks build/watch scripts and adds explicit web bundle + typecheck commands.
extensions/markdown-language-features/esbuild.webview.mts	Switches shared helper import to .mts.
extensions/markdown-language-features/esbuild.notebook.mts	Switches shared helper import to .mts.
extensions/markdown-language-features/esbuild.mts	Switches shared helper import to .mts.
extensions/markdown-language-features/esbuild.browser.mts	Switches shared helper import to .mts.
extensions/ipynb/package.json	Updates notebook build script name.
extensions/ipynb/esbuild.notebook.mts	Switches shared helper import to .mts.
extensions/esbuild-webview-common.mts	Converts webview helper to TS types and exports typed helpers.
extensions/esbuild-extension-common.mts	Adds new shared helper for extension bundling with esbuild.
build/lib/tsgo.ts	Adds noEmit option so build pipeline can typecheck without emitting.
build/lib/extensions.ts	Switches esbuild config filenames to .mts, adds typecheck stream for esbuild builds, and updates media script list.

Comments suppressed due to low confidence (2)

extensions/esbuild-webview-common.mts:8

• The comment says “used in in webviews” (duplicate “in”). Please fix the wording (e.g. “used in webviews”).
  build/lib/extensions.ts:282
• fromLocalEsbuild executes the extension’s esbuild.*.mts script via cp.execFile(process.argv[0], [esbuildScript]) (plain node). Since those scripts now import .mts helpers that include TypeScript-only syntax, this invocation will fail unless Node is started with --experimental-strip-types (or another TS loader). Consider adding the flag when invoking .ts/.mts build scripts here.

	const esbuildScript = path.join(extensionPath, esbuildConfigFileName);

	// Run esbuild, then collect the files
	new Promise<void>((resolve, reject) => {
		const proc = cp.execFile(process.argv[0], [esbuildScript], {}, (error, _stdout, stderr) => {
			if (error) {
				return reject(error);
			}

			const matches = (stderr || '').match(/\> (.+): error: (.+)?/g);
			fancyLog(`Bundled extension: ${ansiColors.yellow(path.join(path.basename(extensionPath), esbuildConfigFileName))} with ${matches ? matches.length : 0} errors.`);