feat: add quiet feature flag to suppress install output

[bri5ee]

Summary

• Adds a quiet compile-time Cargo feature flag to imix that suppresses all Eldritch print/eprint output during ./imix install
• Introduces NoopPrinter in eldritch-core, a Printer implementation that silently discards all output, following the same pattern as StdoutPrinter and BufferPrinter
• When --features quiet is enabled, the install interpreter uses NoopPrinter instead of StdoutPrinter, so embedded tomes run silently with no terminal output

During ./imix install, embedded tomes (e.g. install_service/main.eldritch) print status messages to stdout via the default StdoutPrinter. Imix install stdout might expose how the underlying functionality of the tomes operates for blue teamers if they exfil the imix binary and run it in a sandbox offline. Debug statements are nice to have within the tomes themselves for troubleshooting, but having a functionality at compile-time to go and discard all output would be nice for running ./imix install in prod quickly without having to comment out all of the debug statements in the eldritch files themselves.

This is a compile-time opt-in (quiet is not in the default feature set), so existing builds are unaffected.

Files Changed

• implants/lib/eldritch/eldritch-core/src/interpreter/printer.rs — add NoopPrinter
• implants/lib/eldritch/eldritch-core/src/interpreter/mod.rs — re-export NoopPrinter
• implants/lib/eldritch/eldritch-core/src/lib.rs — re-export NoopPrinter
• implants/lib/eldritch/eldritch/src/lib.rs — re-export NoopPrinter
• implants/imix/Cargo.toml — add quiet feature
• implants/imix/src/install.rs — gate printer selection on quiet feature

[hulto]

LGTM 🚀 🤫