fix: double-click trigger inline renaming

Original commit message(s)

plasma-integration: Folder picker: disable inline rename; expand/collapse via activation (Qt5/Qt6)

• Set NoEditTriggers and disable expandsOnDoubleClick in KFileTreeView
• Keep expansion driven by QAbstractItemView::activated in KDirSelectDialog
• Scope limited to Plasma Integration folder picker; KIO dialogs unchanged

Reason for the change

When using the folder selection dialog through the portal path (e.g. VSCode → xdg-desktop-portal-kde → QFileDialog → Plasma Integration), double-clicking a folder could trigger inline rename instead of expanding/collapsing when the system is set to “Double-click to open.” This conflicts with KDirSelectDialog’s existing logic that toggles expansion via the activated signal.

Root cause:

• QTreeView defaults allow editing on double-click and may also auto-expand on double-click.
• In directory-only selection, rename is not a desired action and competes with activation-driven expansion.

Fix:

• In KFileTreeView (Qt5/Qt6), explicitly disable inline editing with setEditTriggers(QAbstractItemView::NoEditTriggers) and disable implicit expand with setExpandsOnDoubleClick(false).
• Expansion remains driven solely by activated, which already connects to slotExpand(index) in KDirSelectDialog.

Why this is correct:

• Aligns Plasma Integration folder picker behavior with KIO’s folder dialogs (which constrain editing vs activation).
• Prevents unexpected rename operations in a dialog whose purpose is selecting a folder, not managing it.
• Honors the platform SingleClick setting via the activated path, and avoids double-toggling from implicit expand.

Test plan

Manual:

• Toggle System Settings → General Behavior → Click behavior (Single-click vs Double-click).
• From a sandboxed app (e.g. VSCode), File → Open Folder.
• Verify:
  • Double-click expands/collapses items; no rename editor appears.
  • Single-click mode continues to expand/collapse via activation as expected.
  • KIO-based dialogs (non-portal) remain unchanged.

Screenshots or screen recordings

N/A; no visual changes beyond interaction correction.

Bugs fixed

BUG: 324397