fix(cli): support pre-command ultra compact short flag

[YOMXXX]

Summary

• add the documented -u shorthand for ultra-compact mode before the subcommand
• keep -u non-global so git flags like git push -u still pass through
• keep parse errors for unknown leading flags instead of falling back to raw external execution

Fixes #2369

Verification

• cargo +1.93.0 fmt --check
• git diff --check
• cargo +1.93.0 test ultra_compact -- --nocapture
• cargo +1.93.0 test fallback -- --nocapture
• cargo +1.93.0 test git_push_u -- --nocapture
• RTK_TELEMETRY_DISABLED=1 ./target/debug/rtk -u git status --short
• RTK_TELEMETRY_DISABLED=1 ./target/debug/rtk -z grep master
• RTK_TELEMETRY_DISABLED=1 ./target/debug/rtk --help | rg -n -- "ultra|-u|Options"
• cargo +1.93.0 clippy --all-targets
• cargo +1.93.0 test --all -- --skip small_grep_not_worse_than_plain