[Feat] Request cancel in-flight request when new keystroke fires

[PyDevC]

Files: lua/model_cmp/modelapi/request.lua:13-24

Feature Introduction: end_request() and end_all() are defined but never called. Multiple requests can be in-flight simultaneously, wasting server resources and causing stale suggestions to overwrite newer ones.

Feature Description:

1. When the debounce fires a new request, cancel any in-flight request first
2. Call job:shutdown() or uv.kill(job.pid) on the active job
3. Clean up the job entry from M.current_jobs
4. Then start the new request

Is your feature possible with the current status of repo? Yes. end_request() already exists — just needs to be wired into the debounce pipeline in commands.lua.