Add Tishte Serif

**Font Project Git Repo URL:**

https://github.com/yasg1988/tishte-fonts

**Super short description of the Font Family:**

Tishte Serif is a metrically compatible document serif derived from OFL-licensed Tinos, with four static styles, GF Latin Core, Cyrillic, Meadow Mari, and Hill Mari support. It is designed for stable document layout, forms, reports, and multilingual regional publishing.

The reproducible Google Fonts staging build and both current Fontspector and FontBakery reports pass with 0 FAIL, 0 FATAL, and 0 ERROR: https://github.com/yasg1988/tishte-fonts/actions/runs/31353512262

**Requirements:**

By opening this issue, I confirm the project meets the following requirements:

- [x] The entire font project is available in a Github repository (repo) and licensed under the [OFL](https://openfontlicense.org/open-font-license-official-text/)
- [x] I confirm that by 'entire font project', no "plus" or "pro" or other larger version of the project exists as a retail font anywhere
- [x] The source files are available in the repo
- [x] I am the sole copyright author of the entire project, or all other copyright authors have licensed their work to me under the OFL, and I commit to clearly disclosing if AI tools were used in the creation of this project.
- [x] There are no "Reserved Font Names" in the OFL license information, or in the project documentation of any known upstream projects. If there are RFNs, they are not used in whole or in part in this family name, or, I want to discuss how Google can work with my use of them.
- [x] The family name is unique according to [namecheck.fontdata.com](https://namecheck.fontdata.com/)
- [x] The name of the font family expected to appear on app menus must be very clearly communicated and definitive. It should not include any copyright holder's full names or acronyms.
- [x] The font supports at least the Google Fonts 'Latin Core' glyphset from [github.com/googlefonts/glyphsets](https://github.com/googlefonts/glyphsets) ([direct link](https://github.com/googlefonts/glyphsets/blob/main/data/results/txt/nice-names/GF_Latin_Core.txt))
- [x] The repo has the [Google Fonts preferred upstream repo structure](https://googlefonts.github.io/gf-guide/upstream.html)
- [x] I have read, agree with, and comply with, the full [Google Fonts contributing requirements](https://googlefonts.github.io/gf-guide/index#pre-production-getting-your-fonts-ready-for-gf)
- [x] I will maintain the repository and participate in the onboarding process (addressing, solving, and responding to issues, merging pull requests, etc)

**Project and tool disclosure:**

Tishte Serif is derived from the OFL-licensed Tinos project. AI-assisted coding tools were used for engineering automation, quality assurance, and documentation. Glyph provenance is the named OFL upstream project plus the tracked Tishte source and transformation files in the repository.

**Image:**


Start with the linked Tishte Serif repository and the Google Fonts contributing requirements, especially the preferred upstream structure and onboarding process. Review the reproducible staging build and its Fontspector and FontBakery reports first; done means the project passes the required review and onboarding checks for inclusion.

Written by the indexing model from the issue text.