Fix DPI-aware TreeView glyph rendering in Translucent Windows

[63OR63]

Description

Fixes oversized and blurry TreeView expand/collapse chevrons at non-100% display scaling when Windows theme custom rendering is enabled.

The issue is especially noticeable in the File Explorer navigation pane and also occurs with fractional/custom scaling values such as 120%.

Cause

The existing TreeView glyph rendering path has several DPI-related issues:

• Explorer::TreeView detection relies on exact floating-point comparison (width / (16 * scale) == 1), which is unreliable at fractional scaling because the expected size can be fractional while the actual RECT dimensions are integers.
• Glyph geometry is derived from the global DPI scale rather than the actual physical target size.
• Fractionally scaled stroke widths and coordinates can fall between physical pixels, resulting in excessive antialiasing.
• The already-rasterized glyph is passed through DrawNineGridStretch(), introducing another bitmap scaling step.

Fix

The TreeView glyph is now rendered directly at the final physical target size:

• The actual pRect dimensions are passed to CacheTreeViewGlyph().
• Explorer::TreeView detection uses rounded expected physical dimensions instead of exact floating-point equality.
• Vector scale is derived from the actual target dimensions.
• Stroke width is rounded to whole physical pixels and vector coordinates are snapped to the corresponding pixel grid.
• Cached glyphs are recreated when their dimensions don't match the current target.
• The finished bitmap is drawn 1:1 with AlphaBlend() instead of being resized with DrawNineGridStretch().

This avoids resampling an already-rasterized glyph and keeps the chevrons sharp at fractional DPI scaling.

Tested successfully in File Explorer at 100%, custom 120%, 125%, 150%, and 175% display scaling.

Screenshots

Before the fix, at 125% display scaling:

After the fix, at 125% display scaling:

Changelog

• Fixed TreeView expand/collapse chevrons being oversized and blurry at non-100% display scaling.
• Improved TreeView glyph rendering for fractional/custom DPI scaling.