refactor(embedding): 删除无调用的 Token 估算函数

[qin-ptr]

Description

删除截断重构后已无生产调用的 estimate_embedding_input_tokens，以及测试中对它的引用和断言。保留入队前截断的行为验证，无运行时行为变化。

Human Involvement

• A human participated in the implementation or review loop
• This PR was generated entirely by AI agents without human participation in the loop

Related Issue

Related #6129。本 PR 仅清理死代码，不修复真实 Token 超限问题。

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• 删除无生产调用的估算函数。
• 移除测试中的导入、expected_tokens 参数和估算断言，保留截断结果断言。

Testing

• I have added tests that prove my fix is effective or that my feature works

• New and existing unit tests pass locally with my changes

• I have tested this on the following platforms:

  • Linux
  • macOS
  • Windows

• pytest -q --no-cov tests/unit/test_vectorize_file_strategy.py -k bounds_content_before_enqueue：3 passed。

• 修改文件的 ruff check、ruff format --check 和 git diff --check 通过。

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

不涉及。

Additional Notes

无。