in file tree section, include precise offsets to lines in repomix-output.xml

Description

include line offsets to each file's section in repomix-output.xml, so agents can use their read tool with offsets to driectly read the file they want.

something like:

<directory_structure>
src/
  components/
    DictCard.tsx [100:177]
    DictManager.tsx [179:241]
    Editor.tsx
    IssueItem.tsx
    IssueTooltip.tsx
...

to be clear, these are offsets in the current repomix file, not the line numbers in the files themselves.