fix(search): stop clap from capturing -h on rtk grep and rtk rg

[AngelVRodC]

Problem

rtk grep -h pattern file never searched: clap's auto-generated help flag intercepted -h before search.rs could classify it, so rtk printed its own help and exited 0 — a silent false negative. An agent consuming rtk's output sees no matches and no error, and moves on believing the pattern isn't there.

The sibling collisions in #3663 (-l, -m, -t) were already resolved on develop by making rtk's own options long-only. -h outlived them because it was clap's auto-generated help flag rather than a declared option, so dropping a short wasn't possible.

Verified on current develop (d402152): the repro still fires. rtk rg -h is affected the same way — there -h genuinely is rg's --help, but clap prints rtk's help instead of forwarding it.

Fix

#[command(disable_help_flag = true)] on Commands::Grep and Commands::Rg in src/main.rs — 9 lines, comments included.

This removes clap's handling of both -h and --help for those two subcommands. The per-engine check already in search::run then sees the flag and forwards the argv to the engine verbatim:

Command	Before	After
rtk grep -h alpha a.txt	rtk's help, exit 0	alpha, exit 0
rtk grep --help	rtk's help	engine's help, forwarded
rtk rg -h	rtk's help	rg's help, forwarded

Psql and Ctest already carry the same attribute on develop; this applies the established pattern where the same collision exists.

Why so small

This PR previously contained a full per-engine flag-classification rewrite of search.rs (4 commits, ~900 lines). While it sat open, upstream merged that capability via #3988/#3998's arg_tokenizer work — grep_takes_value/rg_takes_value per-engine tables cover the -f, -r, -E, -D, --label, --color fixes this branch originally shipped. Rebased on develop, only the clap -h interception remains unfixed upstream, so the branch was shrunk to exactly that. The old scope is closed; #3665, #3161 and #3881 are resolved by the code already on develop.

Verification

• cargo fmt --all && cargo clippy --all-targets && cargo test --all — clean, 3781 passing
• Repros above verified against native grep 2.6.0-FreeBSD / ripgrep 15.2.0 on macOS (stdout + exit code)
• Common path untouched: rtk rg -n pattern src/ still emits grouped/capped output

Closes #3663

[CLAassistant]

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[KuSh]

Thanks for this. I'm closing it as superseded by #4348, which releases clap's help flag on every wrapper subcommand, grep and rg included. On its head, rtk grep -h alpha a.txt b.txt matches grep byte for byte, and rtk rg -h returns rg's own help.