feat: rename Tkinter dashboard to GUI_V65_Tk, add replay/demo/targets parity

Rename radar_dashboard.py -> GUI_V65_Tk.py and add core feature parity
with the v7 PyQt dashboard while keeping Tkinter as the framework:

Replay mode:
- _ReplayController with threading.Event-based play/pause/stop
- Reuses v7.ReplayEngine and v7.SoftwareFPGA for all 3 input formats
- Dual dispatch routes FPGA control opcodes to SoftwareFPGA during
  raw IQ replay; non-routable opcodes show user-visible status message
- Seek slider with re-emit guard, speed combo, loop checkbox
- close() properly releases engine file handles on stop/reload

Demo mode:
- DemoTarget kinematics scaled to physical range grid (~307m max)
- DemoSimulator generates synthetic RadarFrames with Gaussian blobs
- Targets table (ttk.Treeview) updates from demo target list

Mode exclusion (bidirectional):
- Connect stops active demo/replay before starting acquisition
- Replay load stops previous controller and demo before loading
- Demo start stops active replay; refuses if live-connected
- --live/--replay/--demo in mutually exclusive CLI arg group

Bug fixes:
- seek() now increments past emitted frame to prevent re-emit on resume
- Failed replay load nulls controller ref to prevent dangling state

Tests: 17 new tests for DemoTarget, DemoSimulator, _ReplayController
CI: all 4 jobs pass (167+21+25+29 = 242 tests)

CONTRIBUTING.md

@@ -78,9 +78,9 @@ Every test binary must exit 0.
 
 ```bash
 cd 9_Firmware/9_3_GUI
-python3 -m pytest test_radar_dashboard.py -v
+python3 -m pytest test_GUI_V65_Tk.py -v
 # or without pytest:
-python3 -m unittest test_radar_dashboard -v
+python3 -m unittest test_GUI_V65_Tk -v
 ```
 
 57+ protocol and rendering tests. The `test_record_and_stop` test
@@ -130,7 +130,7 @@ Before pushing, confirm:
 
 1. `bash run_regression.sh` — all phases pass
 2. `make all` (MCU tests) — 20/20 pass
-3. `python3 -m unittest test_radar_dashboard -v` — all pass
+3. `python3 -m unittest test_GUI_V65_Tk -v` — all pass
 4. `python3 validate_mem_files.py` — all checks pass
 5. `python3 compare.py dc && python3 compare_doppler.py stationary && python3 compare_mf.py all`
 6. `git diff --check` — no whitespace issues