unicode,test: add Qwen3.5 non-backtracking tokenizer handler and regr… (#22110)

unicode,test: add Qwen3.5 non-backtracking tokenizer handler and regr… (#22110)

* unicode,test: add Qwen3.5 non-backtracking tokenizer handler and regression tests

- Add unicode_regex_split_custom_qwen35() to [src/unicode.cpp](src/unicode.cpp), a non-backtracking handler for Qwen3.5's [\p{L}\p{M}]+ regex (letters + combining marks).
- Register the handler in the custom tokenizer dispatch table to prevent stack overflows on long inputs (fixes #21919).
- Add [models/ggml-vocab-qwen35.gguf](models/ggml-vocab-qwen35.gguf) (test vocab), [models/ggml-vocab-qwen35.gguf.inp](models/ggml-vocab-qwen35.gguf.inp) (test cases), and [models/ggml-vocab-qwen35.gguf.out](models/ggml-vocab-qwen35.gguf.out) (expected output) for regression testing.
- Update [tests/CMakeLists.txt](tests/CMakeLists.txt) to include the new test entry.

This mirrors the Qwen2 fix (commit 0d049d6), but adapts for Qwen3.5's regex. Ensures robust Unicode tokenization and prevents std::regex stack overflows.

Closes #21919.

* fix: enhance regex handling for Qwen3.5 tokenizer to include accent marks

* cont : remove trailing whitespace

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Co-authored-by: Kabir <redacted>
Co-authored-by: Alde Rojas <redacted>