[codex] Simplify browser target to wasm

[alexstyl]

Summary

Replace the CLI's browser target option with a single explicit wasm target and remove JS target generation from the app template.

Why

The old web option generated both JS and Wasm targets, which was not obvious from the CLI surface and made the generated project model broader than requested. This change makes the browser target explicit and keeps generation aligned with the selected platform.

What changed

• Replace the exposed web target option with wasm in create-app, target, interactive prompts, and dev-template parsing.
• Generate only wasmJs browser target configuration for browser-enabled projects.
• Keep the existing shared webMain resources/source layout used by the Wasm browser app.
• Remove JS-specific root preload wiring and update tests to assert Wasm-only generation.

Validation

• ./gradlew :cli:test --tests com.composables.cli.CliTest
• ./gradlew test
• ./gradlew spotlessCheck
• Generated a scratch app with the browser target and verified both:
  • ./gradlew :composeApp:wasmJsBrowserProductionRun rendered successfully in Chrome headless
  • the built dist/wasmJs/productionExecutable app also rendered successfully when served statically