chore(deps): bump a2a-go v0.3.6 to v0.3.13 (#1599)

## Summary
- Bumps `github.com/a2aproject/a2a-go` from v0.3.6 to v0.3.13
- Updates `KAgentTaskStore.Save` to match the new `a2asrv.TaskStore`
interface which added a `prev *a2a.Task` parameter

Supersedes #1598 (dependabot PR that fails CI due to the breaking
interface change).

## Test plan
- [ ] CI go-lint passes
- [ ] CI go-unit-tests pass
- [ ] CI build (golang-adk) passes

Signed-off-by: Jaison Paul <paul.jaison@gmail.com>

Author: jsonmp-k8

go/adk/pkg/taskstore/store.go

@@ -91,7 +91,7 @@ func cleanPartialArtifacts(artifacts []*a2atype.Artifact) []*a2atype.Artifact {
 }
 
 // Save implements a2asrv.TaskStore.
-func (s *KAgentTaskStore) Save(ctx context.Context, task *a2atype.Task, _ a2atype.Event, _ a2atype.TaskVersion) (a2atype.TaskVersion, error) {
+func (s *KAgentTaskStore) Save(ctx context.Context, task *a2atype.Task, _ a2atype.Event, _ *a2atype.Task, _ a2atype.TaskVersion) (a2atype.TaskVersion, error) {
 	if task == nil {
 		return a2atype.TaskVersionMissing, fmt.Errorf("task cannot be nil")
 	}

go/go.mod

@@ -7,7 +7,7 @@ require (
 	dario.cat/mergo v1.0.2
 
 	// adk dependencies
-	github.com/a2aproject/a2a-go v0.3.6
+	github.com/a2aproject/a2a-go v0.3.13
 	github.com/abiosoft/ishell/v2 v2.0.2
 	github.com/anthropics/anthropic-sdk-go v1.26.0
 	github.com/aws/aws-sdk-go-v2/config v1.32.10

go/go.sum

@@ -22,8 +22,8 @@ github.com/Masterminds/semver/v3 v3.4.0 h1:Zog+i5UMtVoCU8oKka5P7i9q9HgrJeGzI9SA1
 github.com/Masterminds/semver/v3 v3.4.0/go.mod h1:4V+yj/TJE1HU9XfppCwVMZq3I84lprf4nC11bSS5beM=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
 github.com/Microsoft/go-winio v0.6.2/go.mod h1:yd8OoFMLzJbo9gZq8j5qaps8bJ9aShtEA8Ipt1oGCvU=
-github.com/a2aproject/a2a-go v0.3.6 h1:VbRoM2MNsfc7o4GkjGt3KZCjbqILAJq846K1z8rpHTc=
-github.com/a2aproject/a2a-go v0.3.6/go.mod h1:I7Cm+a1oL+UT6zMoP+roaRE5vdfUa1iQGVN8aSOuZ0I=
+github.com/a2aproject/a2a-go v0.3.13 h1:WpIcSHgCySIxD7OQEdV7U7WJc/HL/G2QQj0RJ0YhPi0=
+github.com/a2aproject/a2a-go v0.3.13/go.mod h1:I7Cm+a1oL+UT6zMoP+roaRE5vdfUa1iQGVN8aSOuZ0I=
 github.com/abiosoft/ishell v2.0.0+incompatible h1:zpwIuEHc37EzrsIYah3cpevrIc8Oma7oZPxr03tlmmw=
 github.com/abiosoft/ishell v2.0.0+incompatible/go.mod h1:HQR9AqF2R3P4XXpMpI0NAzgHf/aS6+zVXRj14cVk9qg=
 github.com/abiosoft/ishell/v2 v2.0.2 h1:5qVfGiQISaYM8TkbBl7RFO6MddABoXpATrsFbVI+SNo=