Add --init flag to scaffold a QuickStart ScalaJS project

[Copilot]

Adds a --init <projectName> CLI flag that creates a ready-to-run Laminar/ScalaJS starter project in a subdirectory, then exits — no server started.

What gets scaffolded

Given sjsls --init quickproj, creates:

quickproj/
├── importMap.json       # CDN import map for the `ms` npm package via jsDelivr
├── project.scala        # Scala CLI directives + Laminar app with ms facade
└── assets/
    └── index.less       # Styled LESS stylesheet

Exits with:

Scaffolded app. To run it:
  cd quickproj
  sjsls --styles-dir assets

Changes

• sjsls/src/scaffold.scala (new): template strings for all three files + scaffoldProject(projectName, baseDir) using fs2 to create dirs and write files. Accepts an optional baseDir: Option[Path] (defaults to the process working directory) to support testability.
• sjsls/src/CliOpts.scala: adds initOpt: Opts[String] for --init <string>
• sjsls/src/liveServer.scala: wires initOpt.map(scaffoldProject(_)) as a command alternative alongside the existing version flag
• sjsls/test/src/ScaffoldSpec.scala (new): 4 CatsEffectSuite tests using a temp directory fixture to verify the directory layout is created correctly and that each scaffolded file contains the expected content

[Quafadas]

@copilot please add some tests

[Copilot]

@copilot please add some tests

Added ScaffoldSpec in commit 2c06ca3 with 4 tests:

• directory layout — verifies importMap.json, project.scala, and assets/index.less are all created and ExitCode.Success is returned
• importMap.json content — checks for the @ms@2.1.3/+esm key and jsDelivr CDN URL
• project.scala content — checks for JS platform directive, Laminar dep, ES module kind, import map reference, and the renderOnDomContentLoaded entry point
• index.less content — checks for the @accent LESS variable and the #app selector

I also refactored scaffoldProject to accept an optional baseDir: Option[Path] (defaulting to the process working directory) so tests can pass a temp directory without touching the filesystem at an unpredictable location.