fix(execution): parse DICTEE_FORCE_CPU as truthy, not presence (release 1.3)

cuda_runtime_available() used var_os(...).is_some(), so the value "0"
written by dictee-setup's Force CPU toggle when OFF was still treated as
"force CPU" — silently disabling the GPU for Parakeet/Canary on any user
who opened and applied the ASR settings page (the default state). Parse
"1"/"true"/"yes" as truthy, like the Whisper daemon already does and as
save_config's own comment already claims. Backport of master's existing
implementation. Fixes the v1.3.5 regression introduced with the Force CPU
toggle.

Author: rcspam

src/execution.rs

@@ -207,9 +207,14 @@ impl ModelConfig {
 /// and bypasses ort's own provider-list fallback.
 ///
 /// Honors `DICTEE_FORCE_CPU` as a manual override.
+/// Truthy values that force CPU: "1", "true" / "TRUE", "yes". Anything else
+/// (including "0", "false", "no", empty) means "let me use GPU if available".
 #[cfg(feature = "cuda")]
 pub fn cuda_runtime_available() -> bool {
-    if std::env::var_os("DICTEE_FORCE_CPU").is_some() {
+    if std::env::var("DICTEE_FORCE_CPU")
+        .map(|v| matches!(v.to_ascii_lowercase().as_str(), "1" | "true" | "yes"))
+        .unwrap_or(false)
+    {
         return false;
     }
     // Primary probe: NVIDIA driver populates one dir per GPU under