feat(frontend): Debug -> ROM Info panel (v1.20.0)

[doublegate]

Summary

• New Debug -> ROM Info panel: read-only CRC32/SHA-256/header decode of the loaded cart (crates/rustysnes-frontend/src/debugger/rom_info_panel.rs), following the existing debugger/*.rs panel module pattern.
• RomInfo is captured once per ROM load/close (native OpenRom/CloseRom and the wasm32 file-picker path), not recomputed every frame like DebugSnapshot -- a loaded ROM's identity/header never changes while it stays loaded.
• rustysnes_cart::header::Header gains a decoded title: String field -- Header::parse already had the raw 21-byte title bytes in hand for its own coprocessor-disambiguation title match, this just surfaces them for display.
• Closes the "small catch-up" item named in the 2026-07-15 lockstep-check entry (RustySNES had no ROM Info panel; RustyNES does).

Part of the Phase A UI/UX-parity ladder (see #113/#114/#115 for the sibling wasm-demo/peripheral-input/overscan fixes).

Test plan

• cargo test --workspace --exclude rustysnes-android (475 passed)
• cargo clippy --workspace --exclude rustysnes-android --all-targets -- -D warnings (clean)
• cargo clippy -p rustysnes-frontend --all-targets --features full -- -D warnings (clean)
• Per-feature clippy: debug-hooks, scripting, cheats, netplay, retroachievements, emu-thread (all clean)
• cargo clippy --target wasm32-unknown-unknown -p rustysnes-frontend --no-default-features --features wasm-winit,cheats,debug-hooks -- -D warnings (clean except the confirmed pre-existing save_states.rs::base_dir finding, unrelated to this change)
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --exclude rustysnes-android --no-deps (clean)
• cargo fmt --all --check (clean)
• New unit tests: rustysnes-cart header title decode/trim (2 tests), rom_info_panel::hex_sha256 formatting (1 test)

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces a new read-only "ROM Info" panel to the debugger, displaying key cartridge metadata such as CRC32, SHA-256, board name, map mode, speed, region, coprocessor, ROM/SRAM sizes, and header offsets. The metadata is captured once per ROM load or close to avoid redundant frame-by-frame computations. To support this, the rustysnes_cart::header::Header struct has been updated with a decoded title field, which utilizes a new best-effort ASCII decoding helper. The crc32fast crate has also been added as a dependency to calculate the ROM's CRC32 hash. As there are no review comments provided, I have no additional feedback to offer.

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[Copilot]

Pull request overview

Adds a new Debugger overlay panel to display ROM identity (CRC32/SHA-256) and decoded SNES cart header information, with ROM metadata captured on ROM load/close instead of recomputed each frame. Also surfaces the SNES internal title from the cart header for display and documents the new UI.

Changes:

• Add Debug → ROM Info panel UI and wiring (RomInfo snapshot + panel rendering).
• Capture/store ROM identity/header once per ROM load/close (native + wasm load paths).
• Extend rustysnes_cart::header::Header with a decoded title: String and add unit tests.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
docs/frontend.md	Documents the new ROM Info panel behavior and data sources.
crates/rustysnes-frontend/src/ui_shell.rs	Threads rom_info through shell rendering into the debugger overlay.
crates/rustysnes-frontend/src/debugger/rom_info_panel.rs	New ROM Info panel implementation (field grid + SHA formatting test).
crates/rustysnes-frontend/src/debugger/mod.rs	Registers the new panel and routes rendering based on selected tab.
crates/rustysnes-frontend/src/app.rs	Stores/captures RomInfo on ROM load/close and passes it to the UI.
crates/rustysnes-frontend/Cargo.toml	Adds crc32fast dependency for ROM CRC32 hashing.
crates/rustysnes-cart/src/header.rs	Adds decoded title field to Header and tests for title decode/trim.
CHANGELOG.md	Notes the new ROM Info panel and header title field under Unreleased.
Cargo.lock	Records the added direct dependency linkage for crc32fast.