feat: allow direct entry of slider values

[mondalaci]

Summary

Closes #2795.

Click the value displayed next to a slider to type a number directly, in addition to dragging the slider thumb. Implemented in the shared slider-wrapper component, so all standard sliders get this behavior automatically (e.g. Modules → Trackpad → Base speed, mouse pointer speed, typing behavior timeouts).

Edge cases covered

• Precision beyond slider step — direct entry accepts values finer than the slider thumb step (e.g. 0.85 on a 0.1 step slider).
• Unit suffixes — values with valueUnit (e.g. 1250 px/s) are parsed correctly when typed with or without the unit.
• Number input binding — ngModel on <input type="number"> can bind a number rather than a string; parsing handles both.
• Floating-point round-trips — values that pass through multiply/divide conversions (e.g. mouse move speeds stored as ÷25, displayed as ×25) are normalized to avoid artifacts like 1701.0000000000002.
• Validation — entered values are clamped to min/max; empty/invalid input is discarded.
• Keyboard UX — Enter or blur commits; Escape cancels.
• Disabled sliders — value is not clickable when the slider is disabled.

Out of scope

We do not plan to implement direct entry for the handful of sliders that use a custom valueFormatter for time values (e.g. LED fade timeout shown as 1:30). Those remain slider-only.

Test plan

• Modules → Trackpad → Base speed: click value, enter 0.85, confirm it saves and displays correctly
• Mouse key speed → Acceleration: click value, change 1700 to 1701, confirm no floating-point display artifact
• Mouse key speed with px/s unit: enter value with and without unit suffix
• Press Escape while editing — value reverts; press Enter — value commits
• LED fade timeout slider — value remains read-only (not clickable)

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