server + ui: fix stream routes for model names containing a slash (#26137) server + ui: refactor resumable stream routes to query string conv_id The conversation id can embed a model name containing slashes (ggml-org/...) in router mode, which the decoded path splits before the :conv_id param is captured, so stop and resume never matched the session. Move the id to the conv_id query string on the public routes and on the internal router -> child hop, where slashes survive encoding. Handlers are unchanged since query and path params land in the same map. Add a regression test with a slashed model name.

server: move stream route docs to server-stream.h Address review: ngxson wants the main server.cpp registration code kept clean and simple, with route-level explanations living in the header. Move the query string rationale and the lookup ownership note next to the handler declarations in server-stream.h, and shorten the wiring comment to a pointer. server: cancel a pending request when its stream is stopped during model load The conversation was registered in the conv map only after the blocking autoload wait, so a stop issued while the model loaded found nothing to cancel and the…