fix: vendor deps and fix CI go-version, timeout, GOTOOLCHAIN (HAN-414)

- Run go mod vendor to eliminate proxy.golang.org network dependency
- Set GOFLAGS=-mod=vendor at job env level so all go commands use vendor/
- Fix go-version from 1.23 to 1.24.0 to match go.mod
- Move GOTOOLCHAIN=local to job-level env (not per-step inline)
- Set cache: false on setup-go (cache is irrelevant with vendoring)
- Add timeout-minutes: 15 so failures are caught quickly instead of 3h

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>

vendor/golang.org/x/sys/unix/auxv.go

@@ -0,0 +1,36 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.21 && (aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos)
+
+package unix
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+//go:linkname runtime_getAuxv runtime.getAuxv
+func runtime_getAuxv() []uintptr
+
+// Auxv returns the ELF auxiliary vector as a sequence of key/value pairs.
+// The returned slice is always a fresh copy, owned by the caller.
+// It returns an error on non-ELF platforms, or if the auxiliary vector cannot be accessed,
+// which happens in some locked-down environments and build modes.
+func Auxv() ([][2]uintptr, error) {
+	vec := runtime_getAuxv()
+	vecLen := len(vec)
+
+	if vecLen == 0 {
+		return nil, syscall.ENOENT
+	}
+
+	if vecLen%2 != 0 {
+		return nil, syscall.EINVAL
+	}
+
+	result := make([]uintptr, vecLen)
+	copy(result, vec)
+	return unsafe.Slice((*[2]uintptr)(unsafe.Pointer(&result[0])), vecLen/2), nil
+}