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/modules.txt

@@ -0,0 +1,48 @@
+# github.com/miekg/dns v1.1.72
+## explicit; go 1.24.0
+github.com/miekg/dns
+# golang.org/x/mod v0.31.0
+## explicit; go 1.24.0
+golang.org/x/mod/semver
+# golang.org/x/net v0.48.0
+## explicit; go 1.24.0
+golang.org/x/net/bpf
+golang.org/x/net/idna
+golang.org/x/net/internal/iana
+golang.org/x/net/internal/socket
+golang.org/x/net/ipv4
+golang.org/x/net/ipv6
+# golang.org/x/sync v0.19.0
+## explicit; go 1.24.0
+golang.org/x/sync/errgroup
+# golang.org/x/sys v0.39.0
+## explicit; go 1.24.0
+golang.org/x/sys/unix
+golang.org/x/sys/windows
+# golang.org/x/text v0.32.0
+## explicit; go 1.24.0
+golang.org/x/text/secure/bidirule
+golang.org/x/text/transform
+golang.org/x/text/unicode/bidi
+golang.org/x/text/unicode/norm
+# golang.org/x/tools v0.40.0
+## explicit; go 1.24.0
+golang.org/x/tools/go/ast/edge
+golang.org/x/tools/go/ast/inspector
+golang.org/x/tools/go/gcexportdata
+golang.org/x/tools/go/packages
+golang.org/x/tools/go/types/objectpath
+golang.org/x/tools/go/types/typeutil
+golang.org/x/tools/internal/aliases
+golang.org/x/tools/internal/event
+golang.org/x/tools/internal/event/core
+golang.org/x/tools/internal/event/keys
+golang.org/x/tools/internal/event/label
+golang.org/x/tools/internal/gcimporter
+golang.org/x/tools/internal/gocommand
+golang.org/x/tools/internal/packagesinternal
+golang.org/x/tools/internal/pkgbits
+golang.org/x/tools/internal/stdlib
+golang.org/x/tools/internal/typeparams
+golang.org/x/tools/internal/typesinternal
+golang.org/x/tools/internal/versions