Additional bug fixes and improvements.

Added
- Live zoom sync — changes made via the browser's native Ctrl+- / Ctrl+= now update the extension popup in real time while it's open.
- Slider fill — the portion of the slider from minimum up to the current zoom level is now visually filled with a darker color (light theme) or lighter color (dark theme), making the current value easier to read at a glance.
- +/- buttons next to the slider for fine-grained 1% adjustments.

Fixed
- Zoom applied through the extension now matches the browser's native zoom behavior. Previously, setting a zoom level through the extension could leave responsive sites with broken layouts (content pinned to the left with blank space on the right and bottom). The extension now forces the browser's per-origin automatic zoom mode so pages reflow correctly.
- The extension popup now correctly displays the effective zoom level on initial open, even when the current zoom comes from a per-origin default rather than a tab-level override.
- The "Current zoom" badge is now accurate on pages where a zoom level was previously set via the browser's native controls.