Improve simulator UI, displays, Unicode paths, and SD handling

[oldgamer6753]

Summary

This PR improves the simulator UI, display rendering, Unicode file-path support, SD image handling, and file dialog behavior.

The changes are contained in a single commit and are based directly on the current master.

The implementation is intended to remain cross-platform. Platform-specific handling is used only where required, such as UTF-8 file opening on Windows.
UTF-8-aware file opening is used on Windows via wide-character paths, while the native POSIX file-opening path is preserved on other platforms.

This PR is independent of #61 and does not require the simulator stability / CPU usage changes from that PR.

Changes

Simulator UI

• Start the simulator maximized.
• Open the Display and SD Card component sections by default.
• Keep the Display component above SD Card in the Components list.
• Add Collapse Components List to the main menu to collapse all component sections at once.
• Keep active display popout windows independent of the collapsed / scrolled state of the Components list.
• Add clearer styling to the top-level menu:
  • 1 px #6dcff6 border when not hovered.
  • 10 px spacing between top-level menu items.
  • Preserve the original hover style.
• Replace the File > Quit menu with a direct Exit menu item.
• Rename Break to Debugger Break and move it below the normal simulation controls.
• Always reserve the vertical scrollbar in the Components window to avoid layout oscillation while resizing.

Display rendering

• Add a shared sharp-bilinear framebuffer rendering helper.
• Use sharp bilinear filtering when Integer Scaling is disabled for smoother and cleaner display rendering at non-integer scales.
• Preserve nearest-neighbor rendering when Integer Scaling is enabled.
• Use the shared framebuffer rendering helper for ST7796, HD44780, and ST7920
• Prevent mouse-wheel interaction with an embedded display from blocking Components list scrolling.
• Keep display popout windows visible when their component entry is scrolled out of view or collapsed.

Unicode support

• Embed GNU Unifont 17.0.05 directly in the simulator.
• Add the corresponding OFL license and notice files.
• Improve Cyrillic and other Unicode text rendering without requiring an external font file.
• Add UTF-8-aware file opening on Windows using wide-character paths.
• Keep the non-Windows file-opening path unchanged.

SD Card handling

• Remember the selected SD image path in imgui.ini.
• Reopen the file dialog in the directory of the previously selected image.
• Fall back safely if that directory no longer exists.
• Add SD image validation / audit status:
  • Passed
  • File is missing
  • File is corrupted
• Prevent an invalid SD image from being forced into the Present state.
• Improve the IMG Audit status indicator with a vertically aligned 8×8 px status square.
• Center and enlarge the SD image file dialog.

File dialog

• Update ImGuiFileDialog from 0.6.7 to 0.6.8.
• Enable std::filesystem.
• Enable Escape to close dialogs.
• Enable the Places / Devices pane.
• Improve Windows drive enumeration.
• Allow selecting drives with a single click.
• Suppress unnecessary tooltips for non-editable entries in the Devices pane.

Testing

Tested on:

• Windows 10
• pio run -e simulator_windows
• ST7796 simulator display

Verified:

• Clean build from current upstream/master.
• Simulator starts and runs normally.
• Unicode / Cyrillic SD image paths work.
• SD image path persists across restarts.
• Missing and corrupted SD images are detected correctly.
• File dialog opens in the expected directory.
• Drive selection works correctly.
• Integer Scaling remains pixel-perfect.
• Sharp bilinear rendering works when Integer Scaling is disabled.
• Display popout remains visible while scrolling or collapsing the Components list.
• Collapse Components List works correctly.
• Existing simulator functionality continues to operate normally.

The implementation is intended to remain cross-platform, but this PR has currently only been built and runtime-tested on Windows.

Relation to PR #61

This PR does not depend on #61.

It was rebuilt and tested separately on the current upstream/master without the commit from #61.