fix(tool): enforce the global code search result limit (#1306)

* fix(tool): enforce the global code search result limit

* fix(tool): report matched-file count in code search truncation notice

Scan all git-grep output to count distinct files with text matches instead
of stopping at the 101st match, so the truncation note reports the true
matched-file count and signals that some files are partially shown or omitted.

* feat: Apply suggestion from @lizhengfeng101

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Co-authored-by: kite <lizhengfeng.lzf@alibaba-inc.com>
Co-authored-by: Kite <254839944+lizhengfeng101@users.noreply.github.com>