Score-grid files now land at `<band>/<iso>.prop` with a 4-byte "PROP"
magic header. Readers still accept the legacy `.ntms` extension and
"NTMS" magic so a rolling deploy doesn't invalidate any file already
on the shared NFS mount — legacy files age out through normal
retention.
Applied both sides of the seam: Elixir ScoresFile + regex parsers,
Rust scores_file writer + decoder. Updated the comments in all
modules that mention the extension (NotifyListener, Reconciler,
gefs_fetch_worker, map_live) and the runbook diagram. talos5 is a
DB host now, not a Rust worker — corrected the runbook accordingly.