Feat: keyboard shortcuts reference panel and configurable bindings

[pcolt]

Overview

The app has several keyboard shortcuts with no central place where users can discover or configure them. A shortcuts reference (and eventually a configuration UI) would improve discoverability and let power users adapt bindings to their workflow.

Known shortcuts

Action	Default (Win/Linux)	Default (Mac)	Source
Undo	Ctrl+Z	⌘Z	App.svelte
Redo	Ctrl+Shift+Z or Ctrl+Y	⌘⇧Z	App.svelte
Delete selected node/edge	Backspace / Delete	Backspace / Delete	@xyflow/svelte built-in
Multi-select (box)	Shift+drag	Shift+drag	@xyflow/svelte built-in
Multi-select (click)	Ctrl+click	Cmd+click	@xyflow/svelte built-in

Proposed steps

1. Shortcut reference panel — a read-only list of all bindings, accessible from Settings or a ? button. Platform-aware labels (⌘ on Mac, Ctrl on Win/Linux).
2. Configurable bindings — allow users to remap app-level shortcuts (undo, redo, etc.) via Settings and persist to electron-store. @xyflow built-ins are not remappable without forking the library.

Feasibility notes

• App-level shortcuts (App.svelte keydown handler) are straightforward to make configurable — read the binding from settings, match against e.key + modifier flags.
• @xyflow built-in shortcuts (delete, multi-select) are controlled via the deleteKey, selectionKey, multiSelectionKey props on <SvelteFlow> — these are already configurable if wired to settings values.
• Platform detection: navigator.platform (deprecated but stable in Electron) or navigator.userAgentData.platform.