docs: a portable copy keeps its single-instance socket in %LOCALAPPDATA% (#5260)

apps/pdfcraft/src/single_instance.rs

@@ -4,8 +4,9 @@
 //! Outlook attachments, Explorer double-clicks and Open With all start `pdfcraft.exe "<file>"`, and
 //! a file manager or `xdg-open` starts `pdfcraft <file>` the same way, so until now every file got
 //! its own process and window. The first PdfCraft listens on a Unix domain socket. On Windows (10
-//! 1803 and later) it is in `%LOCALAPPDATA%\PdfCraft`, or in the data folder of a portable copy,
-//! and is named after the Windows session (`instance-Console.sock`), so two sign-ins of the same
+//! 1803 and later) it is in `%LOCALAPPDATA%\PdfCraft` (a portable copy's too, as
+//! `portable-instance-…` and never in its own folder, #889) and is named after the Windows
+//! session (`instance-s1.sock` for session 1), so two sign-ins of the same
 //! user never open files in each other's windows. On Linux and the BSDs it is in
 //! `$XDG_RUNTIME_DIR/pdfcraft` and is named after the display (`instance-wayland-0.sock`), so a
 //! launch on another display or seat opens its own window there. Either way it lives in a folder

crates/ui-egui/src/platform/portable.rs

@@ -1,8 +1,10 @@
 //! Portable mode (#157): a marker file beside the executable ([`MARKERS`]) keeps the settings,
 //! log files, crash-recovery autosaves and new digital IDs in `<exe dir>/PdfCraftData`, so a
-//! portable copy (on a USB stick, say) writes nothing to `%APPDATA%` or `%LOCALAPPDATA%`. The
-//! Windows portable zip ships with `portable.txt`; the MSI doesn't. PhotoCraft uses the same
-//! scheme (`photocraft/apps/photocraft/src/app_dirs.rs`).
+//! portable copy (on a USB stick, say) writes nothing to `%APPDATA%`. In `%LOCALAPPDATA%` it keeps
+//! only its single-instance socket and lock, two empty files in `%LOCALAPPDATA%\PdfCraft` that
+//! must stay private to the user (#889, `apps/pdfcraft/src/single_instance.rs`). The Windows
+//! portable zip ships with `portable.txt`; the MSI doesn't. PhotoCraft uses the same scheme
+//! (`photocraft/apps/photocraft/src/app_dirs.rs`).
 //!
 //! If that folder can't be written (read-only medium, Program Files), portable mode stays off, the
 //! per-user folders are used and the app says why.