lint some of the things

[mxyng]

now that ollama uses go1.22, x/exp/slices can be replaced with regular slices

enable some useful linters:

• intrange is a 1.22 feature which simplifies for i := 0; i < n; i++ { } with for i := range n { }
• testifylint to find bad testify assertions
• unconvert to find unnecessary type conversions
• usestdlibvars to find values that can be replaced with stdlib vars, e.g. OPTIONS with http.MethodOptions
• wastedassign to find unnecessary assignments
• whitespace is find unnecessary line

[bmizerany]

This is far less clear. Let's turn this lint rule off.

From the maintainers of net/http, in summary: "This was a mistake to introduce these constants. It's less clear and readable using them."

[mxyng]

I'm fine turning off the linter however I disagree it's less clear. The var is much easier to search for and less error prone since typos causes build errors.