rsz: document port buffer exception in insertBufferPostProcess

Add a comment explaining why bufferInputs / bufferOutputs pass
loc=nullptr on purpose: port buffers are placed near their BTerm,
which can sit at the die edge outside the core, and that is by
design -- they should stay adjacent to the port.

Makes the `if (loc)` guard self-documenting so future readers do
not wonder whether the nullptr case is a bug.

Comment-only change; no behavioral diff.

Signed-off-by: minjukim55 <mkim@precisioninno.com>

Author: minjukim55

src/rsz/src/Resizer.cc

@@ -5161,6 +5161,11 @@ void Resizer::insertBufferPostProcess(dbInst* buffer_inst,
   // Clamp to core if the caller provided a target location.  ODB's
   // insertBuffer* already placed the instance at *loc; setLocation will
   // re-place it if clamping changed the point.
+  //
+  // Port buffers (bufferInputs / bufferOutputs) intentionally pass
+  // loc=nullptr so we do not clamp them: they are placed near their
+  // BTerm location, which can sit at the die edge outside the core.
+  // That is by design -- port buffers should stay adjacent to the port.
   if (loc) {
     setLocation(buffer_inst, *loc);
   }