Migrate data paths to ~/.local/share/fluorine/, add native build, fix %command% and system Proton scanning

- All data paths migrated from ~/.var/app/com.fluorine.manager/ to
  ~/.local/share/fluorine/ so native and Flatpak builds share the same
  instances, plugins, and configs
- New fluorinepaths.h/.cpp with fluorineDataDir() helper and one-time
  migration from old path (writes MOVED.txt breadcrumb)
- New libs/nak/src/paths.rs as Rust equivalent (data_dir())
- Strip %command% tokens from launch wrapper in protonlauncher.cpp
- Always scan /usr/share/steam/compatibilitytools.d/ for system Proton
  packages (Arch installs Proton there); add Flatpak filesystem permission
- Native build (build-native.sh) installs to ~/.local/share/fluorine/
  with desktop entry and ~/.local/bin symlink instead of portable zip
- build-flatpak.sh wrapper for Flatpak builds
- Fix container locale (LANG=C.UTF-8) for AutoUic warnings
- Fix prefixExists() to handle both compatdata and pfx directory layouts
- Fix globalInstancesRootPath() to use fluorineDataDir() on Linux
- Fix umu-run Flatpak lookup to use fluorineDataDir()
- Update README with build instructions and Arch dependency list

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

6 files changed, 23 insertions, 19 deletions

diff --git a/libs/nak/src/deps/tools.rs b/libs/nak/src/deps/tools.rs
index c97247c..0e3e356 100644
--- a/libs/nak/src/deps/tools.rs
+++ b/libs/nak/src/deps/tools.rs
@@ -1,7 +1,7 @@
 //! Linux tool management (winetricks, cabextract)
 //!
 //! Handles downloading and managing Linux CLI tools.
-//! Tools are stored in ~/.var/app/com.fluorine.manager/bin/ for Fluorine Manager.
+//! Tools are stored in ~/.local/share/fluorine/bin/ for Fluorine Manager.
 
 use std::error::Error;
 use std::fs;
@@ -13,14 +13,13 @@ use std::process::Command;
 use crate::logging::{log_error, log_info, log_warning};
 
 // ============================================================================
-// NaK Bin Directory (~/.var/app/com.fluorine.manager/bin/)
+// NaK Bin Directory (~/.local/share/fluorine/bin/)
 // ============================================================================
 
-/// Get the tool bin directory path (~/.var/app/com.fluorine.manager/bin/)
+/// Get the tool bin directory path (~/.local/share/fluorine/bin/)
 /// This is accessible from both native and Flatpak environments.
 pub fn get_nak_bin_path() -> PathBuf {
-    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
-    PathBuf::from(home).join(".var/app/com.fluorine.manager/bin")
+    crate::paths::data_dir().join("bin")
 }
 
 /// Check if a command exists (either in system PATH or tool bin)
diff --git a/libs/nak/src/dxvk.rs b/libs/nak/src/dxvk.rs
index 97e4222..b335773 100644
--- a/libs/nak/src/dxvk.rs
+++ b/libs/nak/src/dxvk.rs
@@ -1,7 +1,7 @@
 //! DXVK configuration management for Fluorine Manager.
 //!
 //! Downloads dxvk.conf from upstream, appends Fluorine-specific settings,
-//! and stores at `~/.var/app/com.fluorine.manager/config/dxvk.conf`.
+//! and stores at `~/.local/share/fluorine/config/dxvk.conf`.
 
 use std::error::Error;
 use std::fs;
@@ -20,9 +20,7 @@ dxvk.enableGraphicsPipelineLibrary = False
 
 /// Get the path where the DXVK config will be stored.
 pub fn get_dxvk_conf_path() -> PathBuf {
-    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
-    PathBuf::from(home)
-        .join(".var/app/com.fluorine.manager/config/dxvk.conf")
+    crate::paths::data_dir().join("config/dxvk.conf")
 }
 
 /// Ensure the dxvk.conf file exists, downloading if necessary.
diff --git a/libs/nak/src/lib.rs b/libs/nak/src/lib.rs
index c93f07b..59f41c6 100644
--- a/libs/nak/src/lib.rs
+++ b/libs/nak/src/lib.rs
@@ -7,6 +7,7 @@ pub mod config;
 pub mod dxvk;
 pub mod game_finder;
 pub mod logging;
+pub mod paths;
 pub mod runtime_wrap;
 pub mod steam;
 pub mod utils;
diff --git a/libs/nak/src/logging.rs b/libs/nak/src/logging.rs
index 8c0f91a..e506bf8 100644
--- a/libs/nak/src/logging.rs
+++ b/libs/nak/src/logging.rs
@@ -1,7 +1,7 @@
 //! Logging for Fluorine Manager.
 //!
 //! All log messages are:
-//! 1. Written to `~/.var/app/com.fluorine.manager/logs/nak.log` (always)
+//! 1. Written to `~/.local/share/fluorine/logs/nak.log` (always)
 //! 2. Forwarded to an optional callback set via `set_log_callback()` (for MOBase::log)
 
 use std::fs;
@@ -25,8 +25,7 @@ pub fn set_log_callback(cb: impl Fn(&str, &str) + Send + Sync + 'static) {
 
 /// Get the log directory path.
 fn log_dir() -> PathBuf {
-    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
-    PathBuf::from(home).join(".var/app/com.fluorine.manager/logs")
+    crate::paths::data_dir().join("logs")
 }
 
 /// Get the log file path.
diff --git a/libs/nak/src/paths.rs b/libs/nak/src/paths.rs
new file mode 100644
index 0000000..4b212b9
--- /dev/null
+++ b/libs/nak/src/paths.rs
@@ -0,0 +1,12 @@
+//! Shared data directory for Fluorine Manager.
+//!
+//! All data lives under `~/.local/share/fluorine/` — accessible from both
+//! native and Flatpak builds (the Flatpak has `--filesystem=home`).
+
+use std::path::PathBuf;
+
+/// Returns the Fluorine data directory (`~/.local/share/fluorine`).
+pub fn data_dir() -> PathBuf {
+    let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
+    PathBuf::from(home).join(".local/share/fluorine")
+}
diff --git a/libs/nak/src/steam/proton.rs b/libs/nak/src/steam/proton.rs
index 064fd96..4059dc4 100644
--- a/libs/nak/src/steam/proton.rs
+++ b/libs/nak/src/steam/proton.rs
@@ -56,8 +56,6 @@ pub fn find_steam_protons() -> Vec<SteamProton> {
         return protons;
     };
 
-    let is_flatpak = steam_path.to_string_lossy().contains(".var/app/com.valvesoftware.Steam");
-
     // 1. Steam's built-in Protons (steamapps/common/Proton*)
     protons.extend(find_builtin_protons(&steam_path));
 
@@ -65,11 +63,8 @@ pub fn find_steam_protons() -> Vec<SteamProton> {
     protons.extend(find_custom_protons(&steam_path));
 
     // 3. System-level Protons in /usr/share/steam/compatibilitytools.d/
-    if is_flatpak {
-        crate::logging::log_info("Flatpak Steam detected - skipping system protons in /usr/share/steam/compatibilitytools.d/");
-    } else {
-        protons.extend(find_system_protons());
-    }
+    //    (Arch packages Proton here; Flatpak has --filesystem=/usr/share/steam:ro)
+    protons.extend(find_system_protons());
 
     // Filter to only include Proton 10+ (required for Steam-native integration)
     protons.retain(is_proton_10_or_newer);