fix(grpc): support Go 1.25 and 1.26 plugin scenarios

[loon-hejw]

Why

Go 1.25 and Go 1.26 can build the agent at 754482220284, but the existing
plugin runner and gRPC instrumentation leave several compatibility gaps:

• Docker Compose releases newer than v2 are rejected by the scenario runner.
• go mod tidy can rewrite a generated scenario module to go 1.25.0 or
  go 1.26.0 while the generated workspace remains on go 1.25 or go 1.26.
• gRPC v1.81.1 introduces the split genproto RPC module and passes
  *transport.ServerStream to server internals. The current plugin asserts
  *transport.Stream, causing an intercepted panic and fragmented server
  traces. Unary SendResponse spans are also skipped for the new stream type.

What changed

• Add Go 1.25/1.26 Gin and gRPC plugin matrices.
• Accept numeric Docker Compose major versions >= 2.
• Refresh the generated go.work after go mod tidy.
• Move the root monolithic genproto dependency to the first post-split version.
• Match gRPC server streams through their stable Method and Context
  contract instead of a concrete internal type.
• Add focused runner and gRPC interceptor regression tests.

Validation

• go test -race ./plugins/grpc/... ./test/plugins/runner-helper/... ./tools/go-agent/instrument/...
• go test ./...
• Go 1.25.6 and Go 1.26.5 Agent builds for linux/arm64
• Official plugin scenarios:
  • Gin v1.10.1: Go 1.25 and Go 1.26
  • native HTTP: Go 1.25 and Go 1.26
  • gRPC v1.81.1: Go 1.25 and Go 1.26, including unary and all streaming modes
  • Toolkit Trace/Log/Metric activation: Go 1.25 and Go 1.26
  • cross-goroutine context: Go 1.25 and Go 1.26

The baseline gRPC reproduction logs:

interface conversion: interface {} is *transport.ServerStream,
not *transport.Stream

The process survives because the agent recovers the interceptor panic, but the
server streaming trace is split into orphan segments. Both patched Go versions
pass the strict scenario validator without the panic.

[mrproliu]

Please update the changes.md and support-plugins.md

[loon-hejw]

Addressed in commit 918c7f1:

• Updated CHANGES.md with the SpanRef capability, gRPC v1.81.1 support on Go 1.25/1.26, and the recent gRPC server stream compatibility fix.
• Updated docs/en/agent/support-plugins.md to document gRPC support through v1.81.1.

git diff --check passes.

[loon-hejw]

The latest Plugin Tests / mysql (https://github.com/apache/skywalking-go/actions/runs/30410944583/job/90449826435) job failed while pulling the mysql:5.7 image from Docker Hub:

read: connection reset by peer

The failure occurred before the MySQL test scenario started, and the remaining plugin jobs were cancelled by matrix fail-fast. The main CI, Windows plugin tests, and E2E workflows passed.

This appears to be a transient external network failure unrelated to this PR. Could someone with permission please rerun the failed workflow?