feature: Tracer O(1) ring buffer refactor

- Replaced O(n) shift loop + StringCopy/kalloc/kfree with O(1) ring
  buffer storing PChar pointers directly (zero allocation).
- Eliminated mod operator (causes int64 promotion + broken RTL helpers
  on i386 bare-metal); uses pure uint32 branch arithmetic.
- Removed dead code: PTracerEntry/TTracerEntry linked list types,
  head/tail PTracerEntry vars, c_lock boolean
- Dropped lmemorymanager and serial from uses clause
- pop_trace remains as no-op stub for ABI compat
- get_trace_N uses underflow-safe index: if head >= idx then
  head - idx else MAX_TRACE - (idx - head)
- Added print_traces debug helper

src/include/util.pas

@@ -581,12 +581,13 @@ begin
         syslog.writestring('   EIP: '); syslog.writehex(IntSpec^.EIP); syslog.writestring('   CS: '); syslog.writehex(IntSpec^.CS);  syslog.writestring('  EFLAGS: '); syslog.writehexln(IntSpec^.EFLAGS);
         syslog.writestringln(' ');
     end;
-    syslog.writestring('Call Stack: ');
+    tracer.freeze;
+    syslog.writestring('Call Stack:     ');
     trace:= tracer.get_last_trace;
     if trace <> nil then begin
         syslog.writestring('[-0] ');
         syslog.writestringln(trace);
-        for i:=1 to tracer.get_trace_count-7 do begin
+        for i:=1 to tracer.get_trace_count-1 do begin
             trace:= tracer.get_trace_N(i);
             if trace <> nil then begin
                 syslog.writestring('                [');
@@ -594,6 +595,12 @@ begin
                 syslog.writeint(i);
                 syslog.writestring('] ');
                 syslog.writestringln(trace);
+            end else begin
+                syslog.writestring('                [');
+                syslog.writestring('-');
+                syslog.writeint(i);
+                syslog.writestring('] ');
+                syslog.writestringln('?????????');
             end;
         end;
     end else begin