Embed wasm-rtos into the GitHub Pages site

[espmaniac]

Summary

• load the generated Emscripten runtime from os/wasm-rtos.js
• connect the existing drag-and-drop UI to real browser_task_* exports
• replace mock tasks with actual wasm-rtos task state
• wire pause, resume, stop, restart, and remove actions to the runtime
• display runtime initialization, memory, task, queue, and status information
• validate main.js syntax in CI
• commit generated os/wasm-rtos.js and os/wasm-rtos.wasm into the site branch after successful push builds
• continue updating and persisting the top-level os/wasm-rtos submodule pointer

Site behavior

After this PR is merged, a push build generates and commits:

• os/wasm-rtos.js
• os/wasm-rtos.wasm

Because this is the wasm-rtos.github.io user-site repository, GitHub Pages serves those files together with the existing index.html, style.css, and main.js.

Uploaded guest .wasm files are copied into the runtime and launched with the app_main entry point. The site polls real task states and exposes runtime-backed controls.

Validation

Do not merge until the browser build workflow succeeds and the generated runtime files are committed to this branch by the push-triggered workflow run.