readme : refresh (#26280)

readme : refresh (#26280)

* docs : center badges and links, remove Hot topics

- Use <div align="center"> for GitHub-compatible centering
- Add dev branches and compile times links
- Remove Hot topics section

Assisted-by: llama.cpp:Qwen3.6-27B
* readme : remove sections

* docs : center badges, remove Hot topics, extract sections, remove tools

- Use <div align="center"> for GitHub-compatible centering
- Add dev branches and compile times links
- Add lib llama API and llama-server REST API links
- Remove Hot topics section
- Remove Recent API changes section
- Extract XCFramework section into docs/xcframework.md
- Extract Completions section into docs/completions.md
- Extract Obtaining and quantizing models into docs/models.md
- Remove tools usage sections (llama-cli, llama-server, etc.)
- Move Contributing section to the end

Assisted-by: llama.cpp:Qwen3.6-27B
* cont : arrange links

* cont : fix ws

* cont : remove seminal papers

* cont : change sample model

* cont : trim-down contributing section

* cont : sort backends alphabetically

* cont : words

* cont : add fig captions

* docs : models words

* readme : shorter caption

* cont : fix typo

* cont : add window frame to screenshot