feat(theme): hold-to-repeat in the pad editor, its profiles list, and arcade Select

[ddrcoder]

Draft — first of a four-PR stack (this one has no dependencies). Supersedes #689.

Summary

Hold-to-repeat for directional input in three places that only stepped once per press.

• Pad editor (Configure Pads + the Song Select overlay): holding Up/Down/Left/Right repeats, driven by the theme's shared advance_hold_repeat timer. Works in the Simple and Advanced views and in the saved-profiles list. The name box ignores the hold (its Up/Down is a one-shot toggle); any modal, view change, or exit drops it. Shift state is captured at the press so a fine hold stays fine.
• Repeat rate accelerates (the timing from feat(pad-config): keep stepping thresholds while Up/Down is held #689): 300 ms initial delay, then 120 ms shrinking by 12% per repeat down to a 30 ms floor, so a long sweep speeds up without making the first steps twitchy.
• Arcade-navigation Player Options: Select moves to the previous row but never armed the hold timer (Start for next row already repeated), so climbing a long pane meant one tap per row. Select now arms the Up hold on press and releases it, for both sides.

Testing

• New unit tests: repeat timing and release in the pad editor, cursor repeat pausing in modals, profiles-list repeat, held Select in arcade Player Options.
• cargo test -p deadsync-theme-simply-love --lib -- pad_config player_options passes.
• Verified on a cabinet (two SMX pads, arcade navigation on).

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https://claude.ai/code/session_015PLarttSySmaMqrG5uYJHD