fix: single-click zoom now toggles between fit-to-window and 100% pixels

[chuckhenrich]

Description

Single-click zoom previously toggled between fit-to-window and approximately 2× the fit-to-window scale. The zoom target therefore varied with window size and had no fixed reference point, making it difficult to predict where the click would land.

This fix changes single-click to toggle between fit-to-window and 100% zoom (1 image pixel = 1 screen pixel), consistent with standard photo editing tool conventions.

Closes #1638
Closes #1639

Type of Change

• Bug fix
• New feature
• Breaking change
• Performance improvement
• Code refactoring
• Documentation update
• UI/UX improvement
• Build/CI or Dependency update

Changes Made

• src/components/panel/Editor.tsx: Rewrote handleClick toggle logic. The zoom target is now computed as originalSize.width / (baseRenderSize.width * dpr) — the exact internal scale for 100% pixels — rather than Math.min(currentScale * 2, maxScaleRef.current). The toggle condition checks whether the current scale is within 5% of the 100% target rather than using a hardcoded > 1.01 threshold.
• src/components/panel/BottomBar.tsx: Updated currentOriginalPercent to compute from zoom and baseRenderSize.width rather than displaySize.width, ensuring the displayed percentage is consistent with the zoom target used in handleClick.
• src/components/panel/Editor.tsx: Also removes the erroneous Math.max(20, maxScale) floor in transformConfig which was causing the scroll wheel zoom ceiling to scale with window size rather than being fixed at 200% pixels.

Screenshots/Videos

Testing

• These changes were tested locally by a human and confirmed to work.
• I haven't added any automated tests to the code because the codebase currently lacks a test suite.

Test Configuration:

• OS: Ubuntu 24.04 x86_64
• Hardware: Intel 16-thread CPU, GeForce RTX 2060 Rev. A

Checklist

• My code follows the project's code style
• I haven't added unnecessary AI-generated code comments
• My changes generate no new warnings or errors

Additional Notes

The BottomBar.tsx change is a prerequisite for correct display of the 100% zoom level. Without it, floating point drift between the zoom target computation and the display percentage computation caused the display to show 99% instead of 100%.

The maxScale fix (removing Math.max(20, maxScale) in transformConfig) is included in this PR as it was a prerequisite for the correct single-click zoom target computation. It also independently fixes #1638, where the scroll wheel zoom ceiling scaled proportionally with window size rather than being fixed.

AI Disclaimer:

Please state the involvement of AI in this PR:

• This PR is created by an AI agent
• This PR is mostly AI-generated but edited/merged together by a human
• This PR was handwritten with AI assistance (spell check, logic suggestions, error resolving)
• This PR contains only blood, sweat, and coffee (AI-free)