AxonOS Radar 12.0.4

Fixed

• report.html's "Live map" / "Dashboard" / "GitHub" links pointed at
  axonos-radar-core (the private engine, no public Pages site) instead of
  this repo — the same bug patched once before and silently overwritten by
  the next engine sync, because the fix lived in the wrong place. The
  correction now lives in sync_engine_data.py itself, applied to the
  fetched body on every sync before it's ever committed — it survives every
  future sync instead of being undone by it, and becomes a no-op
  automatically once the engine's own template is corrected upstream.
• CONTRIBUTING.md told a new contributor to run
  GH_TOKEN=… python3 scripts/radar.py to refresh data locally — that file
  was deleted at the 8.0.0 open-core cutover, so this was a guaranteed
  FileNotFoundError on the first thing the guide asked anyone to try.
  Replaced with what's actually runnable now (preview, tests, validator)
  and an honest note that discovery/scoring has no local equivalent anymore.
• docs/RETENTION.md attributed retention constants to scripts/radar.py
  (deleted) and radar.yml (disabled) in three separate table rows — all
  three now correctly say the private engine.
• ROADMAP.md's "Where we are" line still said v10.0 while the table two
  lines below it already correctly showed v12.0 shipped — updated the
  summary to match the table it was supposed to summarize.