feat(remap): add cascading action selector

[blak0p]

Closes #78

Summary

• Replaces the flat remap action popup with Basic/Multimedia cascading menus.
• Keeps the menu visible inside scrollable panels and constrains it to the viewport.
• Preserves Button 1 restrictions, staging behavior, and Apply/Discard shortcuts.

Changes

File	Change
frontend/src/components/panels/GnomeSelect.tsx	Adds accessible category/submenu navigation, portal placement, and viewport-aware positioning.
frontend/src/components/panels/GnomeSelect.test.tsx	Covers pointer, keyboard, portal, scroll, and disabled-action behavior.
frontend/src/styles/controls.css	Adds responsive menu/submenu sizing and visibility behavior.
odd/tasks/cascading-remap-selector.md	Records strict-TDD evidence and manual verification.

Hardware impact

No device write, hidraw operation, or Apply action was performed. This is a frontend-only presentation change.

Test Plan

• Focused selector/panel tests — 10 tests
• Full frontend suite — 86 tests
• go test ./... — 313 tests
• go vet ./...
• go build ./... && (cd frontend && npm run build)
• Manual desktop verification of menu visibility and responsive submenu placement

Delivery note

Native reviewer capture was unavailable for this candidate. The maintainer explicitly elected to deliver without native review.