feat(rewrite): strip trailing stderr redirects before pattern matching

Description

rtk rewrite doesn't match commands that have trailing 2>&1 or 2>/dev/null, because the redirect suffix is part of the string passed to pattern matching.

Reproduction

# These match:
rtk rewrite "git status"        # -> rtk git status ✓
rtk rewrite "find . -name '*.ts'"  # -> rtk find . -name '*.ts' ✓

# These don't match (exit 1):
rtk rewrite "git status 2>&1"              # -> no match ✗
rtk rewrite "find . -name '*.ts' 2>&1"     # -> no match ✗
rtk rewrite "ls -la 2>/dev/null"           # -> no match ✗

Impact

Claude Code appends 2>&1 to the vast majority of Bash commands. This means the hook-based rewrite misses most commands that would otherwise match.

From rtk discover on my project: ~975K tokens missed, many from commands that would match if not for the 2>&1 suffix.

Suggested fix

In rtk rewrite, strip trailing 2>&1 / 2>/dev/null before pattern matching, then re-append to the rewritten output.

Workaround: I've added pre-processing to my hook script to strip these before calling rtk rewrite.

Environment

• rtk 0.28.2
• macOS Darwin 25.3.0