Fix incorrect comment: ConPTY sets CTRL_C ignore flag, not Rust runtime

Investigation confirmed Rust std, ctrlc crate, and portable-pty have
zero calls to SetConsoleCtrlHandler(NULL, TRUE). The inheritable ignore
flag is set by the Windows ConPTY subsystem for spawned processes.
The SetConsoleCtrlHandler(None, 0) workaround is still needed — without
it the test times out on Windows — but the comment was wrong about the
source.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: branchseer

crates/pty_terminal/tests/terminal.rs

@@ -305,8 +305,12 @@ fn send_ctrl_c_interrupts_process() {
         // On macOS/Windows, use ctrlc which works fine (no .init_array/musl issue).
         #[cfg(not(target_os = "linux"))]
         {
-            // On Windows, clear the "ignore CTRL_C" flag set by Rust runtime
-            // so that CTRL_C_EVENT reaches the ctrlc handler.
+            // On Windows, an ancestor process may have been created with
+            // CREATE_NEW_PROCESS_GROUP, which implicitly sets the per-process
+            // CTRL_C ignore flag (CONSOLE_IGNORE_CTRL_C in PEB ConsoleFlags).
+            // This flag is inherited by all descendants and silently drops
+            // CTRL_C_EVENT before it reaches registered handlers. Clear it.
+            // Ref: https://learn.microsoft.com/en-us/windows/win32/procthread/process-creation-flags
             #[cfg(windows)]
             {
                 // SAFETY: Declaring correct signature for SetConsoleCtrlHandler from kernel32.

crates/vite_task_bin/src/vtt/exit_on_ctrlc.rs

@@ -3,19 +3,23 @@
 /// Sets up a Ctrl+C handler, emits a "ready" milestone, then waits.
 /// When Ctrl+C is received, prints "ctrl-c received" and exits.
 pub fn run() -> Result<(), Box<dyn std::error::Error>> {
-    // On Windows, Rust's runtime sets `SetConsoleCtrlHandler(NULL, TRUE)` which
-    // ignores CTRL_C_EVENT. This flag is inherited by child processes and takes
-    // precedence over registered handlers. Clear it before registering ours.
+    // On Windows, an ancestor process (e.g. cargo, the test harness) may have
+    // been created with CREATE_NEW_PROCESS_GROUP, which implicitly calls
+    // SetConsoleCtrlHandler(NULL, TRUE) and sets CONSOLE_IGNORE_CTRL_C in the
+    // PEB's ConsoleFlags. This flag is inherited by all descendants and takes
+    // precedence over registered handlers — CTRL_C_EVENT is silently dropped.
+    // Clear it so our handler can fire.
+    // Ref: https://learn.microsoft.com/en-us/windows/win32/procthread/process-creation-flags
     #[cfg(windows)]
     {
-        // SAFETY: Passing (None, FALSE) removes the "ignore CTRL_C" flag.
+        // SAFETY: Passing (None, FALSE) clears the per-process CTRL_C ignore flag.
         unsafe extern "system" {
             fn SetConsoleCtrlHandler(
                 handler: Option<unsafe extern "system" fn(u32) -> i32>,
                 add: i32,
             ) -> i32;
         }
-        // SAFETY: Clearing the Rust runtime's ignore flag.
+        // SAFETY: Clearing the inherited ignore flag.
         unsafe {
             SetConsoleCtrlHandler(None, 0);
         }