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/fdset.go

@@ -0,0 +1,27 @@
+// Copyright 2019 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 aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos
+
+package unix
+
+// Set adds fd to the set fds.
+func (fds *FdSet) Set(fd int) {
+	fds.Bits[fd/NFDBITS] |= (1 << (uintptr(fd) % NFDBITS))
+}
+
+// Clear removes fd from the set fds.
+func (fds *FdSet) Clear(fd int) {
+	fds.Bits[fd/NFDBITS] &^= (1 << (uintptr(fd) % NFDBITS))
+}
+
+// IsSet returns whether fd is in the set fds.
+func (fds *FdSet) IsSet(fd int) bool {
+	return fds.Bits[fd/NFDBITS]&(1<<(uintptr(fd)%NFDBITS)) != 0
+}
+
+// Zero clears the set fds.
+func (fds *FdSet) Zero() {
+	clear(fds.Bits[:])
+}