feat: add process termination codes and SYS_ABORT; whole-process abort() from any thread in libc and montauk-rt

programs/include/montauk/statuscodes.h

@@ -101,6 +101,33 @@ inline const char* GetStatusExplanationText(StatusCode statusCode) {
     return GetStatusText(statusCode);
 }
 
+// Process termination codes: what waitpid returns when the kernel ended the
+// process (crash, kill, abort) instead of it calling exit. 256 + POSIX
+// signal number, so normal exit codes (0..255) can never collide.
+// Analogous to kernel/src/Common/TerminationCodes.hpp; same values.
+typedef enum {
+    TerminationBase = 256,
+    TerminatedIllegalInstruction = TerminationBase + 4,     // SIGILL
+    TerminatedBreakpoint = TerminationBase + 5,             // SIGTRAP
+    TerminatedAborted = TerminationBase + 6,                // SIGABRT
+    TerminatedArithmeticError = TerminationBase + 8,        // SIGFPE
+    TerminatedKilled = TerminationBase + 9,                 // SIGKILL
+    TerminatedAccessViolation = TerminationBase + 11        // SIGSEGV
+} TerminationCode;
+
+// Shared with C (libc.c), so no nullptr. Returns 0 for an unknown code.
+inline const char* GetTerminationText(int exitCode) {
+    switch (exitCode) {
+        case TerminatedIllegalInstruction: return "Illegal instruction";
+        case TerminatedBreakpoint:         return "Breakpoint";
+        case TerminatedAborted:            return "Aborted";
+        case TerminatedArithmeticError:    return "Arithmetic error";
+        case TerminatedKilled:             return "Killed";
+        case TerminatedAccessViolation:    return "Access violation";
+        default:                           return 0;
+    }
+}
+
 #ifdef __cplusplus
 }
 #endif

programs/include/montauk/syscall.h

@@ -527,6 +527,11 @@ namespace montauk {
     inline int kill(int pid) {
         return (int)syscall1(montauk::abi::SYS_KILL, (uint64_t)pid);
     }
+    // End the whole process from any thread (exit code TerminatedAborted).
+    [[noreturn]] inline void abort() {
+        syscall0(montauk::abi::SYS_ABORT);
+        __builtin_unreachable();
+    }
     inline int setsession() {
         return (int)syscall0(montauk::abi::SYS_SETSESSION);
     }