feat(wasm): single-window web entry + trunk harness (issue #45)

The binary now compiles for wasm32 as a runnable web target:

- Split the main-window render into `view_main`, bypassing the
  multi-window id dispatch the browser cannot use.
- Add `run_web` / `boot_web`: a single-window `iced::application`
  entry for wasm (the browser canvas is the only window). Native
  keeps the multi-window `iced::daemon` via cfg-split in `main`.
- Add a `console_error_panic_hook` (wasm-only) for readable panics.
- Add `index.html` + `Trunk.toml` so `trunk serve` builds the wasm
  bundle (no-default-features → no solid3d) with COOP/COEP headers.

Native build and all 75 tests unchanged. Browser runtime (rayon
threads, canvas attach, real file I/O) is the next iteration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.toml

@@ -79,3 +79,6 @@ acadrust = { git = "https://github.com/HakanSeven12/acadrust", branch = "main" }
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 open = "5"
 ureq = { version = "3", default-features = false, features = ["rustls"] }
+
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+console_error_panic_hook = "0.1"