Improve OFDM streaming file throughput recovery

[secup]

Summary

• add LTS-derived OFDM timing offset reporting through the demodulator/waveform interfaces
• retry burst-interleaved OFDM frames with timing correction and support variable-CW OFDM receive paths
• add fixed vs variable OFDM ARQ send paths plus single-frame FILE_BLOCK file payload support
• update high-throughput OFDM window/SACK/ACK policy and focused tests

Hardware throughput notes

10KB file, SNR 20, injected channel, Sound Blaster/USB hardware path:

Channel	Rate	Result	Data goodput	Retx	Frame success
AWGN	R1/4	PASS	435.8 bps	0	100.0%
AWGN	R1/2	PASS	1261.4 bps	0	100.0%
AWGN	R3/4	PASS	2101.2 bps	0	100.0%
good	R1/4	PASS	429.6 bps	0	100.0%
good	R1/2	PASS	1029.7 bps	1	100.0%
good	R3/4	PASS	1018.1 bps	20	100.0%
moderate	R1/4	PASS	413.0 bps	8	100.0%
moderate	R1/2	PASS	1229.9 bps	0	100.0%
moderate	R3/4	PASS	384.9 bps	79	98.8%

Tests

• cmake --build build --target test_connection_policy test_file_transfer_controller -j4
• build/tests/test_connection_policy
• build/tests/test_file_transfer_controller
• build/tests/test_frame_v2
• build/tests/test_streaming_config
• build/tests/test_streaming_decode_policy
• build/tests/test_ofdm_link_adaptation