records: exclude indoor/treadmill/virtual sub_sport; rebuild athlete.json on bake

- fit.py: map FIT sub_sport 'treadmill' and 'virtual' to 'indoor'
- writer.py: broaden _is_outdoor to catch all indoor sub_sport variants
- render/cli.py: rebuild athlete.json from index.json on every bake so
  records never go stale when the exclusion logic changes

bincio/extract/parsers/fit.py

@@ -147,11 +147,13 @@ def _normalise_sub_sport(value: Any) -> str | None:
     mapping = {
         "generic":           None,       # FIT default — unspecified
         "virtual_activity":  "indoor",
+        "virtual":           "indoor",
         "road":              "road",
         "mountain":          "mountain",
         "gravel_cycling":    "gravel",
         "cyclocross":        "gravel",
         "indoor_cycling":    "indoor",
+        "treadmill":         "indoor",
         "trail":             "trail",
         "track":             "track",
         "cross_country_skiing": "nordic",