Fix folder ThemeIcon causing incorrect tree level inset

[Copilot]

Description

A custom tree view parent item using ThemeIcon("folder") rendered its children at the wrong tree-level inset, while any other icon aligned correctly.

Root cause: Aligner.hasIcon in treeView.ts decided whether an item "has an icon" by deferring file/folder ThemeIcons to the file icon theme (folder required hasFileIcons && hasFolderIcons). But TreeRenderer actually draws a file/folder ThemeIcon as an always-present codicon whenever the item has no resource (per shouldShowThemeIcon). The mismatch made alignIconWithTwisty treat the parent as icon-less and pick the wrong branch, shifting the children's inset.

Changes:

• Aligner.hasIcon — treat any ThemeIcon that renders as a codicon as having an icon, mirroring the renderer:

// Any other ThemeIcon, or a `file`/`folder` ThemeIcon on an item without a resource,
// is always rendered as a codicon and therefore always has an icon.
if (node.themeIcon && (!node.resourceUri || (node.themeIcon.id !== FileThemeIcon.id && node.themeIcon.id !== FolderThemeIcon.id))) {
    return true;
}

file/folder icons on items that do have a resource still defer to the file icon theme, unchanged.