server : move chat-template thinking probe inside the init try/catch (#24093)

A model whose chat template parses at init but fails parser generation at apply time (e.g. uses {% call %}) throws std::invalid_argument from common_chat_templates_support_enable_thinking(), which ran outside the try/catch guarding common_chat_templates_init(). The throw was uncaught and llama-cli aborted (SIGABRT) instead of failing to load. Moved the probe inside that try/catch so an apply-time error fails load the same way an init parse error does.

Signed-off-by: Jesse LaRose [email protected]