improve configs, update docs

extract_config.example.yaml

@@ -31,6 +31,16 @@ classifier:
 
 incremental: true         # skip files whose hash hasn't changed since last run
 
+# ── Platform importers ─────────────────────────────────────────────────────────
+# Credentials for `bincio import strava`.
+# Get them from strava.com/settings/api (2 minutes, no approval needed).
+# Authorization Callback Domain must be set to: localhost
+# import:
+#   strava:
+#     client_id: 12345
+#     client_secret: your_client_secret_here
+
+# ── Athlete zones ───────────────────────────────────────────────────────────────
 # athlete:
 #   max_hr: 182              # used to derive default HR zone display
 #   ftp_w: 280               # functional threshold power in watts