fix(behaviors): Ignore masked mods in key repeat

[jjiill888]

When a mod-morph consumes a modifier, it masks it via zmk_hid_masked_modifiers_set() so the morphed keycode is sent without it. The key repeat behavior, however, captured zmk_hid_get_explicit_mods() unfiltered and stored it as implicit modifiers, and implicit modifiers bypass the mask when the HID report is built.

Pressing shift, tapping a mod-morph that morphs to an unshifted keycode (e.g. COMMA -> SEMICOLON), releasing shift and then pressing &key_repeat therefore emitted ':' instead of a second ';'.

Expose the masked modifiers and exclude them when capturing, so only modifiers that actually contributed to the output are repeated.

Fixes #3368

PR check-list

• Branch has a clean commit history
• Additional tests are included, if changing behaviors/core code that is testable.
• Proper Copyright + License headers added to applicable files (Generally, we stick to "The ZMK Contributors" for copyrights to help avoid churn when files get edited)
• Pre-commit used to check formatting of files, commit messages, etc.
• Includes any necessary documentation changes.