fix(grep): rtk grep -v inverts match instead of bumping verbose (closes #1477)

[tiagodocouto]

What

rtk grep -v foo file returned matching lines instead of inverting them (#1477). verbose is a global flag with short -v, so clap consumed -v before the grep subcommand could see it. Only --invert-match worked.

Why not just a local -v

Adding #[arg(short = 'v', long = "invert-match")] to the Grep subcommand panics at startup — clap requires unique short names (verified against clap 4.6):

Command grep: Short option names must be unique for each argument,
but '-v' is in use by both 'invert_match' and 'verbose'

Change (two parts)

1. Native --invert-match flag (long-only) on the grep subcommand, forwarded to ripgrep. clap parses it in any position. (A bare --invert-match before the positionals would otherwise be an UnknownArgument, since extra_args is trailing_var_arg.)
2. argv rewrite for the -v shorthand: a standalone -v token after the grep subcommand becomes --invert-match before parsing. Scoped carefully:
   • -v before grep (rtk -v grep ...) stays verbose.
   • a -- separator stops the rewrite, so rtk grep -- -v searches for the literal -v (GNU grep / getopt convention).
   • --verbose remains available for a verbose grep.

Verification

• cargo build, cargo clippy --all-targets --all-features -- -D warnings, cargo fmt --all -- --check — all clean
• cargo test — full suite green; 8 new unit tests for the rewrite + parse
• smoke (real binary, rtk filter path — not the raw-grep fallback): rtk grep -v apple file → inverted + filtered; rtk grep apple file -v → inverted; rtk grep apple file → unchanged; rtk grep -- -v file → literal search

Closes #1477