FUSE VFS performance, tracked writes fix, remove steam-run, add NixOS flake

- FUSE: disable AUTO_INVAL_DATA, enable readdirplus, 24h TTLs, clone_fd,
  FUSE_USE_VERSION=312 — cuts game load time from 2:40 to 1:57
- Fix tracked writes going to wrong (lower-priority) mod in both
  detectManualMoves and syncOverwrite
- Remove steam-run entirely (UI, C++, Rust layers)
- Build system: default to tarball, add installer/appimage as opt-in modes
- Add flake.nix for NixOS — builds from source with Rust crates as
  separate pure derivations, FHS wrapper, NixOS module with FUSE passthrough

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

1 files changed, 0 insertions, 27 deletions

diff --git a/libs/nak/src/runtime_wrap.rs b/libs/nak/src/runtime_wrap.rs
index 69f693e..37980d3 100644
--- a/libs/nak/src/runtime_wrap.rs
+++ b/libs/nak/src/runtime_wrap.rs
@@ -1,38 +1,11 @@
-use std::env;
 use std::ffi::OsStr;
 use std::process::Command;
 
-fn env_flag(name: &str) -> bool {
-    matches!(
-        env::var(name)
-            .unwrap_or_default()
-            .trim()
-            .to_ascii_lowercase()
-            .as_str(),
-        "1" | "true" | "yes" | "on"
-    )
-}
-
-pub fn use_steam_run() -> bool {
-    env_flag("NAK_USE_STEAM_RUN")
-}
-
 /// Build a command to run `exe` with the given environment variables.
-///
-/// In steam-run mode, the command is wrapped with `steam-run`.
-/// Otherwise the command runs directly.
 pub fn build_command<S: AsRef<OsStr>>(
     exe: impl AsRef<OsStr>,
     envs: &[(&str, S)],
 ) -> Command {
-    if use_steam_run() {
-        let mut cmd = Command::new("steam-run");
-        cmd.arg(exe.as_ref());
-        for (key, value) in envs {
-            cmd.env(key, value.as_ref());
-        }
-        return cmd;
-    }
     let mut cmd = Command::new(exe);
     for (key, value) in envs {
         cmd.env(key, value.as_ref());