Restore orchestration user opt-out gate

[nkoorty]

Motivation

• A recent change removed the persisted orchestration opt-out which caused orchestration to be considered enabled whenever OrchestrationV2 and global AI were on, re-exposing StartAgent tooling and bypassing user consent.
• The change restores explicit user control so prior opt-outs continue to prevent advertising/execution of orchestration tools.

Description

• Reintroduced the orchestration_enabled setting in AISettings with TOML key agents.warp_agent.other.orchestration_enabled and feature_flag: FeatureFlag::OrchestrationV2 so the persisted user preference is loaded again (app/src/settings/ai.rs).
• Updated AISettings::is_orchestration_enabled() to require all three conditions: FeatureFlag::OrchestrationV2 enabled, AI globally enabled, and *self.orchestration_enabled (user opt-in) (app/src/settings/ai.rs).
• Added a unit test orchestration_user_opt_out_disables_orchestration_even_when_v2_is_enabled and renamed the existing positive test to reflect both flag and user setting interaction (app/src/settings/ai_tests.rs).
• Applied code formatting with cargo fmt --all.

Testing

• Ran cargo fmt --all and it completed successfully.
• Added/updated unit tests: a positive-path test for v2+AI+user setting, a negative-path test for user opt-out, and a negative-path test for the v2 flag being off (located in app/src/settings/ai_tests.rs).
• Attempted cargo test -p warp orchestration_v2 --lib; a build was started but dependency compilation did not complete within this environment (long compile), so the full test run did not finish here.
• An initial attempt to run cargo test against -p app failed because that package name does not exist in the workspace in this environment.

---

Codex Task