Add FUSE external mapping support, BG3/Oblivion Remastered fixes, fomod-plus and NaK integration

FUSE VFS now deploys non-data-dir mod mappings (Paks, OBSE, UE4SS, etc.)
via real symlinks and injects file-level data-dir mappings (plugins.txt,
loadorder.txt) into the VFS tree. Fixes game launches for Oblivion
Remastered (Root Builder path resolution, script extender support) and
BG3 (Wine prefix documents directory, file mapper symlinks on Linux).

Vendors mo2-fomod-plus plugin and NaK crate for FOMOD installer and
game finder/runtime support.

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

1 files changed, 154 insertions, 0 deletions

diff --git a/libs/nak/src/config.rs b/libs/nak/src/config.rs
new file mode 100644
index 0000000..62f9fc5
--- /dev/null
+++ b/libs/nak/src/config.rs
@@ -0,0 +1,154 @@
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::PathBuf;
+
+fn get_home() -> String {
+    std::env::var("HOME").unwrap_or_default()
+}
+
+/// Normalize a path for compatibility with pressure-vessel/Steam container.
+///
+/// On Fedora Atomic/Bazzite/Silverblue, $HOME is `/var/home/user` but `/home`
+/// is a symlink to `/var/home`. Pressure-vessel exposes `/home` but may not
+/// properly handle paths that explicitly use `/var/home/`. This function
+/// converts such paths to use `/home/` instead for maximum compatibility.
+pub fn normalize_path_for_steam(path: &str) -> String {
+    // Convert /var/home/user/... to /home/user/...
+    if let Some(stripped) = path.strip_prefix("/var/home/") {
+        format!("/home/{}", stripped)
+    } else {
+        path.to_string()
+    }
+}
+
+fn default_data_path() -> String {
+    format!("{}/NaK", get_home())
+}
+
+// ============================================================================
+// Main App Config - stored in ~/.config/nak/config.json
+// ============================================================================
+
+#[derive(Serialize, Deserialize, Clone)]
+pub struct AppConfig {
+    pub selected_proton: Option<String>,
+    /// Whether the first-run setup has been completed
+    #[serde(default)]
+    pub first_run_completed: bool,
+    /// Path to NaK data folder (legacy ~/NaK - used for migration detection)
+    #[serde(default = "default_data_path")]
+    pub data_path: String,
+    /// Whether the Steam-native migration popup has been shown
+    #[serde(default)]
+    pub steam_migration_shown: bool,
+    /// Custom cache location (for downloads, tmp files during install)
+    /// If empty/not set, uses ~/.cache/nak/
+    #[serde(default)]
+    pub cache_location: String,
+    /// Selected Steam account ID (Steam3 format, e.g., "910757758")
+    /// If empty/not set, uses the most recently active account
+    #[serde(default)]
+    pub selected_steam_account: String,
+}
+
+impl Default for AppConfig {
+    fn default() -> Self {
+        Self {
+            selected_proton: None,
+            first_run_completed: false,
+            data_path: default_data_path(),
+            steam_migration_shown: false,
+            cache_location: String::new(),
+            selected_steam_account: String::new(),
+        }
+    }
+}
+
+impl AppConfig {
+    /// Config file path: ~/.config/nak/config.json
+    fn get_config_path() -> PathBuf {
+        PathBuf::from(format!("{}/.config/nak/config.json", get_home()))
+    }
+
+    /// Legacy config path for migration: ~/NaK/config.json
+    fn get_legacy_path() -> PathBuf {
+        PathBuf::from(format!("{}/NaK/config.json", get_home()))
+    }
+
+    pub fn load() -> Self {
+        let config_path = Self::get_config_path();
+        let legacy_path = Self::get_legacy_path();
+
+        // Try new location first
+        if config_path.exists() {
+            if let Ok(content) = fs::read_to_string(&config_path) {
+                if let Ok(config) = serde_json::from_str(&content) {
+                    return config;
+                }
+            }
+        }
+
+        // Try legacy location and migrate if found
+        if legacy_path.exists() {
+            if let Ok(content) = fs::read_to_string(&legacy_path) {
+                if let Ok(mut config) = serde_json::from_str::<AppConfig>(&content) {
+                    // Ensure data_path is set (old configs won't have it)
+                    if config.data_path.is_empty() {
+                        config.data_path = default_data_path();
+                    }
+                    // Save to new location
+                    config.save();
+                    // Remove old config
+                    let _ = fs::remove_file(&legacy_path);
+                    return config;
+                }
+            }
+        }
+
+        Self::default()
+    }
+
+    pub fn save(&self) {
+        let path = Self::get_config_path();
+        if let Some(parent) = path.parent() {
+            let _ = fs::create_dir_all(parent);
+        }
+        if let Ok(json) = serde_json::to_string_pretty(self) {
+            let _ = fs::write(path, json);
+        }
+    }
+
+    /// Get the NaK data directory path (legacy ~/NaK - used for migration detection)
+    pub fn get_data_path(&self) -> PathBuf {
+        PathBuf::from(&self.data_path)
+    }
+
+    /// Get the NaK config directory (~/.config/nak/)
+    pub fn get_config_dir() -> PathBuf {
+        PathBuf::from(format!("{}/.config/nak", get_home()))
+    }
+
+    /// Get the default cache directory (~/.cache/nak/)
+    pub fn get_default_cache_dir() -> PathBuf {
+        PathBuf::from(format!("{}/.cache/nak", get_home()))
+    }
+
+    /// Get the cache directory (custom location or default ~/.cache/nak/)
+    pub fn get_cache_dir(&self) -> PathBuf {
+        if self.cache_location.is_empty() {
+            Self::get_default_cache_dir()
+        } else {
+            PathBuf::from(&self.cache_location)
+        }
+    }
+
+    /// Get path to tmp directory (~/.cache/nak/tmp/)
+    pub fn get_tmp_path() -> PathBuf {
+        Self::get_default_cache_dir().join("tmp")
+    }
+
+    /// Get path to Prefixes directory (legacy - for migration detection only)
+    pub fn get_prefixes_path(&self) -> PathBuf {
+        self.get_data_path().join("Prefixes")
+    }
+}