ci+fix: UCRT time functions on Windows; skip libsnappy on MinGW; NUL-terminated names in the mt test

- timeformat node: localtime_s/gmtime_s (reversed args, 64-bit time_t)
  on Windows — MinGW has no localtime_r/gmtime_r
- the multithread suite test passed non-NUL-terminated property names
  (str::as_ptr) to the C property suite — UB that resolved to garbage
  lookups on the CI runner
- libsnappy off on the MinGW FFmpeg build (only feeds the hap encoder;
  its pkg-config entry does not reach the static link)

crates/oaknode/src/nodes/timeformat.rs

@@ -67,11 +67,18 @@ struct Tm {
 
 // `localtime_r` / `gmtime_r` (C `time.h`). Declared locally instead of
 // pulling in a libc crate; both symbols live in the platform C library
-// that `std` already links.
+// that `std` already links. Windows (UCRT) has the `_s` variants with
+// reversed argument order and a 64-bit time_t.
+#[cfg(not(target_os = "windows"))]
 extern "C" {
 	fn localtime_r(timep: *const c_long, result: *mut Tm) -> *mut Tm;
 	fn gmtime_r(timep: *const c_long, result: *mut Tm) -> *mut Tm;
 }
+#[cfg(target_os = "windows")]
+extern "C" {
+	fn localtime_s(result: *mut Tm, timep: *const i64) -> i32;
+	fn gmtime_s(result: *mut Tm, timep: *const i64) -> i32;
+}
 
 /// Expand Qt date/time format tokens (`QDateTime::toString` syntax):
 /// the field tokens d/dd, M/MM, yy/yyyy, h/hh, H/HH, m/mm, s/ss, z/zz/zzz,
@@ -287,6 +294,7 @@ impl NodeBehavior for TimeFormatNode {
 		let ms = (ms_since_epoch % 1000) as i32;
 
 		let mut tm: Tm = unsafe { std::mem::zeroed() };
+		#[cfg(not(target_os = "windows"))]
 		unsafe {
 			if to_bool(&local_val) {
 				localtime_r(&secs, &mut tm);
@@ -294,6 +302,15 @@ impl NodeBehavior for TimeFormatNode {
 				gmtime_r(&secs, &mut tm);
 			}
 		}
+		#[cfg(target_os = "windows")]
+		unsafe {
+			let secs64 = secs as i64;
+			if to_bool(&local_val) {
+				localtime_s(&mut tm, &secs64);
+			} else {
+				gmtime_s(&mut tm, &secs64);
+			}
+		}
 
 		let output = format_date_time(&tm, ms, &to_text(&format_val));
 		table.push(crate::value::ValueType::Text, NodeValue::Text(output), None);