fix(blastware_file, server): implement logic to skip extra chunks after metadata for accurate file writing

sfm/server.py

@@ -885,14 +885,18 @@ def device_event_blastware_file(
         def _do():
             with _build_client(port, baud, host, tcp_port, timeout=120.0) as client:
                 info = client.connect()
-                # Use stop_after_metadata=True (full_waveform=False) with 0 extra
-                # chunks after "Project:".  Confirmed from 4-26-26 BW RS-232 capture
-                # of "copy event to file" on a 2-sec Continuous event (key=01110000):
-                # BW sends the termination frame IMMEDIATELY after the chunk that
-                # contains "Project:" — no extra chunk is downloaded first.
-                # extra_chunks_after_metadata=1 was WRONG: it downloaded one additional
-                # chunk (counter = last_data_counter + 0x0400) adding ~1053 spurious
-                # bytes to the body, causing Blastware to reject the file.
+                # Use stop_after_metadata=True (full_waveform=False) with 1 extra
+                # chunk after "Project:".  The extra chunk is required to prime the
+                # device over TCP: termination at term_counter=metadata_counter+0x0400
+                # returns only ~90 bytes (no useful footer) over TCP/cellular, but
+                # termination at metadata_counter+0x0800 (one chunk later) returns
+                # the full 737-byte frame containing the footer.
+                #
+                # Confirmed from 4-26-26 BW RS-232 capture: BW terminates at 0x1800
+                # without an extra chunk (works on RS-232 but not TCP).
+                # write_blastware_file() automatically skips the extra chunk's
+                # contribution — only the probe+ADC+metadata+terminator bytes appear
+                # in the output file.
                 #
                 # full_waveform=True (natural end-of-stream) downloads ALL chunks
                 # including post-event silence (35+ chunks for a 9-sec event at
@@ -900,7 +904,7 @@ def device_event_blastware_file(
                 events = client.get_events(
                     full_waveform=False,
                     stop_after_index=index,
-                    extra_chunks_after_metadata=0,
+                    extra_chunks_after_metadata=1,
                 )
                 matching = [ev for ev in events if ev.index == index]
                 return matching[0] if matching else None, info