Flatpak Steam does not recreate ~/.steam symlinks after apt Steam uninstall — all games fail silently

Steps to reproduce:
1. Install Steam via apt (sudo apt install steam)
2. Install Steam via Flatpak (flatpak install flathub com.valvesoftware.Steam)
3. Uninstall apt Steam (sudo apt remove steam / apt purge)
→ apt's postrm scripts delete ~/.steam and ~/.local/share/Steam
4. Continue using Flatpak Steam — it never recreates the symlinks
5. All games fail to launch (exit code 255, silent to user)

Root cause:
steam-runtime-steam-remote inside pressure-vessel cannot find
the Steam IPC socket without ~/.steam/root → actual install path.
Flatpak Steam only creates these symlinks on first install, not on
subsequent launches if they go missing.

Environment:
- OS: Debian 13 (trixie), kernel 6.12.90+deb13-amd64
- Flatpak: 1.16.6
- Steam Flatpak: 1.0.0.85 (stable, flathub)
- GPU: AMD RX 6950 XT, Mesa 25.0.7-2

Fix: manually recreate symlinks pointing to Flatpak data dir

Start by reproducing the apt uninstall followed by Flatpak Steam launch, checking ~/.steam/root and ~/.local/share/Steam and the Flatpak data directory. Trace the Flatpak Steam startup or initialization logic that creates these links; done means missing links are recreated automatically and games launch instead of failing silently with exit code 255.

Written by the indexing model from the issue text.