cl: report makeslice len/cap panic before indexing

[cpunion]

Fixes the fixedbugs/issue37975 makeslice panic-text group.

Changes:

• checks dynamic makeslice len/cap before constructing the slice so cap/len errors are reported at make time
• adds stable test/go coverage for makeslice len/cap panic text
• removes verified xfail entries for fixedbugs/issue37975.go

Local verification from the worker:

• go test ./test/go -run TestMakeSlicePanicText -count=1
• go test ./cl -run 'TestIntVal|TestIsAllocVargs' -count=1\n- go test ./ssa -run Test -count=1\n- go run ./cmd/llgo run $(go env GOROOT)/test/fixedbugs/issue37975.go\n- go run ./cmd/llgo test -run TestMakeSlicePanicText ./test/go\n- go run ./cmd/llgo test -run 'Test(MakeSlicePanicText|FullSliceBoundsPanicText)' ./test/go\n- go test ./cl -run TestRunAndTestFromTestrt -count=1\n- Go 1.24/1.25/1.26 TestGoRootRunCases for fixedbugs/issue37975.go with empty xfail\n\nGC/liveness/finalizer/goroutine cases are intentionally untouched.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 88.57143% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cl/compile.go	88.57%	2 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!