fix(grep): handle Windows drive-letter paths and CRLF in parseOutput

The grep tool's content and count output modes always returned 'No
matches found' on Windows due to two issues:

1. Regex ^(.+?):(\d+):(.*)$ fails on Windows paths like
   C:\path\file.ts:42:content because lazy .+? matches only 'C',
   then \d+ fails on '\path\...'

2. ripgrep outputs CRLF line endings on Windows. After split('\n'),
   trailing \r breaks the $ anchor in the regex, causing every
   line to fail matching.

Fix: update parseOutput and parseCountOutput regexes to handle
drive-letter prefixes ([A-Za-z]:[\/]), and strip trailing \r
from each line before matching.

Note: PR #2976 attempted to fix (1) with --path-separator=/ but
this flag gets expanded by MSYS2/Git Bash to a full path, causing
a separate rg error. This PR avoids --path-separator entirely.

Closes #2962