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/net/ipv6/endpoint.go

@@ -0,0 +1,127 @@
+// Copyright 2013 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.
+
+package ipv6
+
+import (
+	"net"
+	"time"
+
+	"golang.org/x/net/internal/socket"
+)
+
+// BUG(mikio): On Windows, the JoinSourceSpecificGroup,
+// LeaveSourceSpecificGroup, ExcludeSourceSpecificGroup and
+// IncludeSourceSpecificGroup methods of PacketConn are not
+// implemented.
+
+// A Conn represents a network endpoint that uses IPv6 transport.
+// It allows to set basic IP-level socket options such as traffic
+// class and hop limit.
+type Conn struct {
+	genericOpt
+}
+
+type genericOpt struct {
+	*socket.Conn
+}
+
+func (c *genericOpt) ok() bool { return c != nil && c.Conn != nil }
+
+// PathMTU returns a path MTU value for the destination associated
+// with the endpoint.
+func (c *Conn) PathMTU() (int, error) {
+	if !c.ok() {
+		return 0, errInvalidConn
+	}
+	so, ok := sockOpts[ssoPathMTU]
+	if !ok {
+		return 0, errNotImplemented
+	}
+	_, mtu, err := so.getMTUInfo(c.Conn)
+	if err != nil {
+		return 0, err
+	}
+	return mtu, nil
+}
+
+// NewConn returns a new Conn.
+func NewConn(c net.Conn) *Conn {
+	cc, _ := socket.NewConn(c)
+	return &Conn{
+		genericOpt: genericOpt{Conn: cc},
+	}
+}
+
+// A PacketConn represents a packet network endpoint that uses IPv6
+// transport. It is used to control several IP-level socket options
+// including IPv6 header manipulation. It also provides datagram
+// based network I/O methods specific to the IPv6 and higher layer
+// protocols such as OSPF, GRE, and UDP.
+type PacketConn struct {
+	genericOpt
+	dgramOpt
+	payloadHandler
+}
+
+type dgramOpt struct {
+	*socket.Conn
+}
+
+func (c *dgramOpt) ok() bool { return c != nil && c.Conn != nil }
+
+// SetControlMessage allows to receive the per packet basis IP-level
+// socket options.
+func (c *PacketConn) SetControlMessage(cf ControlFlags, on bool) error {
+	if !c.payloadHandler.ok() {
+		return errInvalidConn
+	}
+	return setControlMessage(c.dgramOpt.Conn, &c.payloadHandler.rawOpt, cf, on)
+}
+
+// SetDeadline sets the read and write deadlines associated with the
+// endpoint.
+func (c *PacketConn) SetDeadline(t time.Time) error {
+	if !c.payloadHandler.ok() {
+		return errInvalidConn
+	}
+	return c.payloadHandler.SetDeadline(t)
+}
+
+// SetReadDeadline sets the read deadline associated with the
+// endpoint.
+func (c *PacketConn) SetReadDeadline(t time.Time) error {
+	if !c.payloadHandler.ok() {
+		return errInvalidConn
+	}
+	return c.payloadHandler.SetReadDeadline(t)
+}
+
+// SetWriteDeadline sets the write deadline associated with the
+// endpoint.
+func (c *PacketConn) SetWriteDeadline(t time.Time) error {
+	if !c.payloadHandler.ok() {
+		return errInvalidConn
+	}
+	return c.payloadHandler.SetWriteDeadline(t)
+}
+
+// Close closes the endpoint.
+func (c *PacketConn) Close() error {
+	if !c.payloadHandler.ok() {
+		return errInvalidConn
+	}
+	return c.payloadHandler.Close()
+}
+
+// NewPacketConn returns a new PacketConn using c as its underlying
+// transport.
+func NewPacketConn(c net.PacketConn) *PacketConn {
+	cc, _ := socket.NewConn(c.(net.Conn))
+	return &PacketConn{
+		genericOpt:     genericOpt{Conn: cc},
+		dgramOpt:       dgramOpt{Conn: cc},
+		payloadHandler: payloadHandler{PacketConn: c, Conn: cc},
+	}
+}