Summary

This fixes a keyboard shortcut edge case where duplicate saved bindings can leave a key non-functional or unreliable at runtime.

Problem

Shortcut bindings are loaded from settings without conflict resolution. If two actions end up saved with the same key, ShortcutManager rebuilds multiple QShortcuts for that key. In practice that can make the key behave ambiguously.

One real example was:

• mode_lsb = L
• lock_toggle = L

That let USB work with its unique binding while LSB appeared broken.

Fix

During ShortcutManager load, normalize duplicate key assignments before shortcuts are rebuilt:

• keep the first unique binding for each key
• if a duplicate exists, prefer an explicit customized binding over a default binding
• clear the losing duplicate and save the normalized settings back out

Why this is low risk

• only affects invalid duplicate bindings already present in saved settings
• does not change normal shortcut behavior for valid unique bindings
• uses existing QtCore APIs only, with no dependency or build-system changes

Validation

• reproduced the issue by inspecting saved shortcut settings with both mode_lsb and lock_toggle bound to L
• isolated the fix onto a clean branch from main
• verified the branch contains only the ShortcutManager change