Auto-mode sessions now probe local git state and report telemetry

Autonomous "auto mode" sessions now run a git-state probe that collects the current branch, default branch, remote visibility (public/private), working-copy status, and a Chrome navigation classifier baseline. This feeds into an internal context payload, and completion fires tengu_auto_mode_git_state_probe telemetry with timing, an outcome classification such as clean, dirty, or no_status, and truncation flags. It also flags when the collected context exceeds a byte ceiling.