fix(middleware): restore LF endings and cover tool_choice parsing with specs

The previous commit on this branch saved core/http/middleware/request.go
with CRLF line endings, ballooning the diff against master to 684 / 651
for what is in reality a ~50-line parsing change. Restore LF (matches
.editorconfig end_of_line = lf).

Add 11 Ginkgo specs under "SetModelAndConfig tool_choice parsing
(chat completions)" that parallel the existing MergeOpenResponsesConfig
specs from #9509. They drive the full middleware chain (SetModelAndConfig
+ SetOpenAIRequest) and assert:

  * "required"  -> ShouldUseFunctions=true, no specific name
  * "none"      -> ShouldUseFunctions=false (tools disabled per OpenAI spec)
  * "auto"      -> default, tools available, no specific name
  * {type:function, function:{name:X}}  (spec)    -> X is forced
  * {type:function, name:X}             (legacy)  -> X is forced
  * nested wins when both forms are present
  * malformed shapes (no type, wrong type, no name, empty name) are no-ops

Update the inline comment on the string case to describe the actual
mechanism: "none" reaches SetFunctionCallString("none") downstream and
is then honored by ShouldUseFunctions() returning false. Before this PR
json.Unmarshal([]byte("none"), &functions.Tool{}) failed silently, so
"none" was ignored - making "none" actually work is a real behavior fix
this PR brings.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:opus-4-7 [Claude Code]

Author: mudler