feat(protocol): enhance raw capture functionality and documentation updates

- Update `s3_bridge.py` to default raw capture file paths to "auto" for timestamped naming.
- Modify `gui_bridge.py` to pre-check raw capture options and streamline path handling.
- Extend `ach_server.py` to save both incoming and outgoing raw bytes for analysis.
- Revise `CHANGELOG.md` and `instantel_protocol_reference.md` to reflect changes in recording mode handling and compliance data encoding.

bridges/s3-bridge/s3_bridge.py

@@ -390,8 +390,14 @@ def main() -> int:
     ap.add_argument("--s3", default="COM5", help="S3-side COM port (default: COM5)")
     ap.add_argument("--baud", type=int, default=38400, help="Baud rate (default: 38400)")
     ap.add_argument("--logdir", default=".", help="Directory to write session logs into (default: .)")
-    ap.add_argument("--raw-bw", default=None, help="Optional file to append raw bytes sent from BW->S3 (no headers)")
-    ap.add_argument("--raw-s3", default=None, help="Optional file to append raw bytes sent from S3->BW (no headers)")
+    ap.add_argument("--raw-bw", default="auto",
+                    help="File to append raw bytes sent from BW->S3 (no headers). "
+                         "Default 'auto' generates a timestamped name in --logdir. "
+                         "Pass an empty string to disable.")
+    ap.add_argument("--raw-s3", default="auto",
+                    help="File to append raw bytes sent from S3->BW (no headers). "
+                         "Default 'auto' generates a timestamped name in --logdir. "
+                         "Pass an empty string to disable.")
     ap.add_argument("--quiet", action="store_true", help="No console heartbeat output")
     ap.add_argument("--status-every", type=float, default=0.0, help="Seconds between console heartbeat lines (default: 0 = off)")
     args = ap.parse_args()
@@ -414,12 +420,16 @@ def main() -> int:
     # If raw tap flags were passed without a path (bare --raw-bw / --raw-s3),
     # or if the sentinel value "auto" is used, generate a timestamped name.
     # If a specific path was provided, use it as-is (caller's responsibility).
-    raw_bw_path = args.raw_bw
-    raw_s3_path = args.raw_s3
-    if raw_bw_path in (None, "", "auto"):
-        raw_bw_path = os.path.join(args.logdir, f"raw_bw_{ts}.bin") if args.raw_bw is not None else None
-    if raw_s3_path in (None, "", "auto"):
-        raw_s3_path = os.path.join(args.logdir, f"raw_s3_{ts}.bin") if args.raw_s3 is not None else None
+    # Resolve raw tap paths.
+    # "auto" (default) → timestamped file in logdir (always captured).
+    # Explicit path     → use verbatim.
+    # None or ""        → disabled (pass --raw-bw "" to suppress capture).
+    raw_bw_path: Optional[str] = args.raw_bw if args.raw_bw else None
+    raw_s3_path: Optional[str] = args.raw_s3 if args.raw_s3 else None
+    if raw_bw_path == "auto":
+        raw_bw_path = os.path.join(args.logdir, f"raw_bw_{ts}.bin")
+    if raw_s3_path == "auto":
+        raw_s3_path = os.path.join(args.logdir, f"raw_s3_{ts}.bin")
 
     logger = SessionLogger(log_path, bin_path, raw_bw_path=raw_bw_path, raw_s3_path=raw_s3_path)