[mgwedd]

Summary

• run_fallback in src/main.rs called std::env::args(), which aborts the process when any argument is not valid UTF-8. Clap rejects such args first and routes to the fallback, so rtk grep -c $'\xc3\xa2\xe2\x80' reliably aborted with exit 134 before the wrapped command ever ran.
• The fallback now collects args_os() into a Vec<OsString> and passes those to the wrapped command, so the original bytes reach it unchanged; a lossy Vec<String> is derived only for the display, tracking, and TOML-filter-lookup strings. restore_double_dash in src/core/args_utils.rs had the same env::args() call and got the same treatment. No std::env::args() calls remain in src/.
• Converting everything with to_string_lossy would also have stopped the abort, but it would have silently replaced the bytes passed to the underlying command. The raw OsStrings are kept on the execution path deliberately; the second test below pins that behavior.

Fixes #3025.

Test plan

• cargo fmt --all && cargo clippy --all-targets && cargo test
• Manual testing: rtk <command> output inspected

New tests/non_utf8_argv_test.rs (unix-only, since Windows argv is UTF-16) adds two tests:

• non_utf8_arg_does_not_abort — asserts rtk doesn't panic or get killed by a signal when given a non-UTF-8 argument. This is how I reprod the reported panic initially.
• non_utf8_arg_reaches_the_wrapped_command_verbatim — proves the invalid bytes reach the wrapped command unchanged (would fail if the fix used a lossy conversion instead of keeping raw OsStrings).

Both tests were red on develop baseline and green after this fix.

Gate results: cargo fmt --all --check clean, cargo clippy --all-targets no warnings, cargo test --all 2566 passed / 0 failed. rtk printf '%s' hello still behaves normally.

[rtk-release-bot]

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[rtk-release-bot]

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