Qwen 3.5 tool call grammar (#346)

* Add Qwen3.5 VLM tool-call guard

* Harden native tool-call grammars

* Align native tool grammars with parser syntax

* Simplify native argument grammars

* Use native Qwen tool-call separator

* Reject Qwen structural tags in parameter values

* Require single-token Qwen tool markers

* Keep Gemma tool names adjacent to arguments

* Disallow spaces after Qwen function marker

* Ignore non-object Qwen tool declarations

* Apply pre-commit formatting

* Read only the first Qwen tools block