Launcher --sudo probe: File.Exists check before ConnectAsync

v6.0.1 fix for HANDSHAKE-MISS false positives on cold-start sudo. Launcher/Program.cs checks File.Exists('\.\pipe\wkappbot_elevated') BEFORE ConnectAsync. If pipe file is absent, admin Eye hasn't been spawned yet (cold start) -- quiet fallthrough to Core which will handle UAC + SudoHandler.EnsureAdminForSudo. If pipe file EXISTS but ConnectAsync fails, real zombie -- that's when we fire the HANDSHAKE MISS banner + bug-auto suggest. Previous fastFailMs=100 elapsed-based heuristic mis-classified every cold-start as handshake miss (merged 34x in 33h). Keeps v6.0 pipe separation: wkappbot_eye_ipc (normal Eye tick) and wkappbot_elevated (admin Eye cmd proxy) must never mix. Affects --all commands via --sudo flag.

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