Function is_dev_self 

pub fn is_dev_self() -> bool

True iff THIS binary is a source-tree / task dev build, determined from the binary’s path + portable marker via RuntimeMode::current_path_only — NOT from AGENTMUX_RUNTIME_MODE. A running task dev AgentMux exports AGENTMUX_RUNTIME_MODE=dev:<branch> into its environment, which every descendant process inherits; a packaged build launched from a terminal / agent pane inside a dev instance would otherwise mis-identify as Dev (e.g. the “DEV” status-bar badge on a release build). Build identity is a property of the binary on disk, not of whoever launched it.

Use for build-identity self-checks (the DEV badge, the “AgentMux DEV” menu name, the dev-only frontend fallback). For intra-instance plumbing that must agree with the launcher’s already-made decision, use RuntimeMode::from_env instead.