macOS: honor stable Nix defaults suite (#12205)

* macOS: honor Nix defaults suite; auto launch in Nix mode

Fixes repeated onboarding in Nix deployments by detecting nixMode from the stable defaults suite (ai.openclaw.mac) and bridging key settings into the current defaults domain.

Also enables LaunchAgent autostart by default in Nix mode (escape hatch: openclaw.nixAutoLaunchAtLogin=false).

* macOS: keep Nix mode fix focused

Drop the automatic launch-at-login behavior from the Nix defaults patch; keep this PR scoped to reliable nixMode detection + defaults bridging.

* macOS: simplify nixMode fix

Remove the defaults-bridging helper and rely on a single, stable defaults suite (ai.openclaw.mac) for nixMode detection when running as an app bundle. This keeps the fix focused on onboarding suppression and rename churn resilience.

* macOS: fix nixMode defaults suite churn (#12205)

CHANGELOG.md

@@ -36,6 +36,7 @@ Docs: https://docs.openclaw.ai
 - State dir: honor `OPENCLAW_STATE_DIR` for default device identity and canvas storage paths. (#4824) Thanks @kossoy.
 - Doctor/State dir: suppress repeated legacy migration warnings only for valid symlink mirrors, while keeping warnings for empty or invalid legacy trees. (#11709) Thanks @gumadeiras.
 - Tests: harden flaky hotspots by removing timer sleeps, consolidating onboarding provider-auth coverage, and improving memory test realism. (#11598) Thanks @gumadeiras.
+- macOS: honor Nix-managed defaults suite (`ai.openclaw.mac`) for nixMode to prevent onboarding from reappearing after bundle-id churn. (#12205) Thanks @joshp123.
 
 ## 2026.2.6