fix: resolve correctness bugs and improve robustness

[cymoo]

• fix(path): replace concrete type switch with reflect.Kind so named type aliases (e.g. type UserID int) work correctly with Path[T]
• fix(path): normalize catch-all pattern keys by stripping trailing ... so /files/{path...} extracts via r.PathValue("path") as expected
• fix(result): write error status and JSON body code consistently when Result.Err is set; Result.Code is now used as the explicit override
• fix(headers): use setHeaderIfMissing so a Content-Type set in Result.Headers is not overwritten by automatic response handling
• fix(handler): validate unsupported parameter types at H() registration time instead of panicking on the first request
• fix(handler): allow Responder as a valid single-value interface return; allow http.Handler/io.Reader/Responder as first interface return in two-value signatures
• fix(writer): add Unwrap() to ResponseWriter for net/http compatibility with optional-interface discovery (e.g. http.NewResponseController)
• fix(config): lock mutex inside Initialize's sync.Once to be consistent with Configure/Reset; use logger() instead of log.Println for 5xx logs
• fix(validation): extend default tag name lookup order to json→schema→form so schema-tagged query/form fields appear correctly in error messages
• test: add targeted tests for each of the above issues

[Copilot]

Pull request overview

This PR tightens Mint’s request/response correctness and robustness, primarily around handler signature validation, path param extraction, response header/error handling, and config/validation defaults, with targeted tests added to lock in behavior.

Changes:

• Fixes Path[T] extraction for named underlying types and catch-all ({name...}) patterns.
• Makes response writing more consistent (error code/body alignment; don’t overwrite user-provided Content-Type; add ResponseWriter.Unwrap).
• Validates handler signatures/parameter types earlier in H(...) and expands allowed interface return types; extends validator tag-name resolution to json → schema → form.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
README.md	Updates documented default validator tag-name behavior to include schema.
mint.go	Core fixes across path extraction, handler validation, response writing/error handling, config locking, and validation tag lookup.
mint_test.go	Adds regression tests covering the fixed behaviors (Path aliases/catch-all, Result error consistency, content-type preservation, Unwrap, schema tag naming, etc.).
.github/copilot-instructions.md	Adds repo-specific developer guidance and commands (needs alignment with updated behavior).

Comments suppressed due to low confidence (1)

mint.go:534

• The new fn == nil guard only catches a nil interface. If the caller passes a typed-nil function value (e.g. var f func(...)=nil; H(f)), reflect.ValueOf succeeds but the first request will panic when calling the nil function. Consider also checking fnVal.Kind() == reflect.Func && fnVal.IsNil() and panicking early with a clear message.

func H(fn any) http.HandlerFunc {
	if fn == nil {
		log.Panic("H: handler must be a function, got <nil>")
	}

	fnVal := reflect.ValueOf(fn)
	fnType := fnVal.Type()

	if fnType.Kind() != reflect.Func {
		log.Panicf("H: handler must be a function, got %T", fn)
	}

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.