fix: regenerate golden hex for dual-16pt Doppler and add real-data TBs to regression

Regenerate all real-data golden reference hex files against the current
dual 16-point FFT Doppler architecture (staggered-PRI sub-frames).
The old hex files were generated against the previous 32-point single-FFT
architecture and caused 2048/2048 mismatches in both strict real-data TBs.

Changes:
- Regenerate doppler_ref_i/q.hex, fullchain_doppler_ref_i/q.hex, and all
  downstream golden files (MTI, DC notch, CFAR) via golden_reference.py
- Add tb_doppler_realdata (exact-match, ADI CN0566 data) to regression
- Add tb_fullchain_realdata (exact-match, decim->Doppler chain) to regression
- Both TBs now pass: 2048/2048 bins exact match, MAX_ERROR=0
- Update CI comment: 23 -> 25 testbenches
- Fill in STALE_NOTICE.md with regeneration instructions

Regression: 25/25 pass, 0 fail, 0 skip. ruff check: 0 errors.

.github/workflows/ci-tests.yml

@@ -67,7 +67,7 @@ jobs:
         working-directory: 9_Firmware/9_1_Microcontroller/tests
 
   # ===========================================================================
-  # FPGA RTL Regression (23 testbenches + lint)
+  # FPGA RTL Regression (25 testbenches + lint)
   # ===========================================================================
   fpga-regression:
     name: FPGA Regression