feat: shortcut-registry

[gjermundgaraba]

Background

I wanted to add a shortcut, and when I started to look into the code, I felt an enormous itch to not add another shortcut until there was a more sustainable solution. So, I spent a few good hours on it over the weekend to try to design a usable system.

I am more than happy to iterate on this, if this is something you are interested in :)

Sorry for the amount of code in this PR, but I wanted to make a proper solution ^^

Summary

• Introduces a centralized keyboard shortcut registry (packages/ui/shortcuts/) with typed scope definitions, a binding parser, and runtime dispatcher — replacing scattered ad-hoc keydown handlers across the codebase
• Migrates plan editor, review editor, and shared UI components to use registry-based shortcuts
• KeyboardShortcuts.tsx help modal now renders dynamically from the registry instead of hardcoded lists
• Each app (editor, review-editor) defines its own shortcut scopes and composes them into a surface-level registry
• Marketing site gets an Astro component that auto-generates shortcut reference docs from the registry

[backnotprop]

Going to have a look!