CONTRIBUTING.md contains unreplaced project name placeholders

Describe the bug

CONTRIBUTING.md still contains four unreplaced {project_name} placeholders. Two of them are used in the Issues and Pull Requests URLs, so those links currently return HTTP 404. The other two make the fork and pull-request destination instructions ambiguous.

To Reproduce

1. Open CONTRIBUTING.md on the default branch.
2. Follow the "Github Issues" link under "How to Find Known Issues" or the "GitHub" link under "Submit a Pull Request".
3. Observe that the URL points to coze-dev/{project_name} and returns 404.
4. Search the file for {project_name} and observe four remaining occurrences.

Expected behavior

The contribution guide should name coze-dev/coze-studio (and the coze-studio:main PR target) directly so its links and instructions are actionable.

Screenshots

Not applicable; the two affected URLs return HTTP 404.

Version:

Default branch main, commit fefb05ff27be1da939612fbf9faf5db62583b8ae.

Environment:

Not applicable; this is a documentation issue reproducible in a browser.

Additional context

I searched open and closed issues and pull requests for the literal URL, placeholder wording, and broken CONTRIBUTING.md links, and found no existing report or patch.