Add Rust/WASM WebUI with WebUSB Gowin programming

[ArthurHeymans]

Summary

• Refactor CLI protocol/chip parsing into shared library modules for reuse by WASM
• Add Trunk/egui WebUI using WebSerial for NORbert runtime operations
• Add WebUSB Gowin/Tang Primer 25K loader using ftdi-nusb feat/wasm-webusb for SRAM and external flash bitstream programming
• Add GitHub Actions for CI, Pages deployment, FPGA bitstream artifacts, and release artifacts

Notes

• The WebUSB FPGA loader depends on the ftdi-nusb feat/wasm-webusb branch, which has also been pushed to ArthurHeymans/ftdi-nusb.
• External flash programming is implemented via the GW5A JTAG-SPI path and exposes verify/unprotect/chip-erase options in the WebUI.

Validation

• cargo fmt --manifest-path tool/Cargo.toml --all -- --check
• cargo check --manifest-path tool/Cargo.toml --target wasm32-unknown-unknown --no-default-features --features web --bin norbert-web
• RUSTC="$(rustup which --toolchain nightly rustc)" CARGO_TARGET_DIR=tool/target-validate-web-nightly rustup run nightly cargo clippy --manifest-path tool/Cargo.toml --target wasm32-unknown-unknown --no-default-features --features web --bin norbert-web -- -D warnings
• nix develop --command sh -c 'cd tool && trunk build --release'
• nix develop --command sh -c 'CARGO_TARGET_DIR=tool/target-validate-cli cargo test --manifest-path tool/Cargo.toml --no-default-features --features cli'