DL-237
app.toml is client-only: absent or mode="client" → client (server_url required); mode="embedded" is a legible retirement error, never a compatibility arm; the --mode/$COMPASS_APP_MODE override retires with the second mode. Supersedes the embedded-default mode-selection half of DL-109 (whose keychain-first bearer clause stays Active)
Status: Superseded by DL-320 (Matt, 2026-09-01)
Record: ../../ui/compass-native-client-only/design.md#a3–appconfig-the-clean-cut-client-is-the-only-mode