fix: correct saving of custom file paths

[nnothing1]

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en: In the package template, adding {{.ProjectDir}} introduced absolute paths,
but file generation still used relative paths, which resulted in incorrect
paths like "/path/to/rel/path/to/rel". This change normalizes path handling
during processing to ensure generated file paths are correct.

zh(optional): 在 package 模板中 添加 {{.ProjectDir}} ，会给path带上绝对路径，但是生成文件时又按相对路径生成，从而导致路径不正确（“/path/to/rel/path/to/rel ”绝对路径套绝对路径），因此在 handle 时统一路径格式，确保生成文件路径正确。

(Optional) Which issue(s) this PR fixes:

Fixes #1428

(Optional) The PR that updates user documentation:

[HeyJavaBean]

lgtm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.98%. Comparing base (b2a99fc) to head (a38697c).
⚠️ Report is 5 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1434      +/-   ##
===========================================
+ Coverage    74.16%   74.98%   +0.82%     
===========================================
  Files          147      147              
  Lines        16988    14190    -2798     
===========================================
- Hits         12599    10641    -1958     
+ Misses        3794     2954     -840     
  Partials       595      595              

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