feat(tui-go): workflow-propose choice panel

Render a workflow.proposed frame as a single-select picker with a manual-answer
slot: ↑↓/jk to choose, enter to launch, e for custom, esc to peek away. Picking
a candidate sends StartSession (and focuses the launched session); the custom
slot continues the conversation via ChatInput. Reuses the modal helpers from the
clarification view.

apps/tui-go/internal/protocol/golden_test.go

@@ -149,6 +149,25 @@ func TestDecodeGoldenServerFrames(t *testing.T) {
 				}
 			},
 		},
+		{
+			name: "workflow.proposed carries candidate workflows",
+			json: `{"type":"workflow.proposed","sessionId":"s1","proposalId":"prop-1","prompt":"Run one?",` +
+				`"candidates":[{"workflowId":"research","reason":"gather + report"},{"workflowId":"role_pipeline","reason":""}],` +
+				`"originalRequest":"find papers","sequence":9,"sessionSequence":4}`,
+			wantType:  TypeWorkflowProposed,
+			eventBear: true,
+			check: func(t *testing.T, m ServerMessage) {
+				if m.ProposalID != "prop-1" || m.Prompt != "Run one?" || m.OriginalRequest != "find papers" {
+					t.Fatalf("workflow.proposed fields: %+v", m)
+				}
+				if len(m.Candidates) != 2 {
+					t.Fatalf("workflow.proposed candidates: %+v", m.Candidates)
+				}
+				if m.Candidates[0].WorkflowID != "research" || m.Candidates[0].Reason != "gather + report" {
+					t.Fatalf("workflow.proposed candidate[0]: %+v", m.Candidates[0])
+				}
+			},
+		},
 		{
 			name: "clarification.required carries structured questions",
 			json: `{"type":"clarification.required","sessionId":"s1","requestId":"req-1","stageId":"analyst",` +

apps/tui-go/internal/protocol/protocol.go

@@ -35,6 +35,7 @@ const (
 	TypeApprovalRequired = "approval.required"
 	TypeApprovalResolved = "approval.resolved"
 	TypeClarification    = "clarification.required"
+	TypeWorkflowProposed = "workflow.proposed"
 	TypeWorkspaceBound   = "session.workspace_bound"
 	TypeStageManifest    = "stage.tool_manifest"
 	TypeProviderStatus   = "provider.status_changed"
@@ -139,6 +140,19 @@ type ServerMessage struct {
 
 	// clarification.required — open questions a stage raised for the operator
 	Questions []ClarificationQuestionDto `json:"questions"`
+
+	// workflow.proposed — the router's triage suggestion of candidate workflows
+	ProposalID      string                `json:"proposalId"`
+	Prompt          string                `json:"prompt"`
+	OriginalRequest string                `json:"originalRequest"`
+	Candidates      []ProposedWorkflowDto `json:"candidates"`
+}
+
+// ProposedWorkflowDto is one candidate workflow the router suggests, with a short
+// reason. Mirrors the Kotlin ProposedWorkflow (core:events), the wire shape.
+type ProposedWorkflowDto struct {
+	WorkflowID string `json:"workflowId"`
+	Reason     string `json:"reason"`
 }
 
 // ClarificationQuestionDto is one open question from a stage. Empty Options ->
@@ -313,6 +327,7 @@ func (m ServerMessage) IsEventBearing() bool {
 		TypeToolStarted, TypeToolCompleted, TypeToolFailed, TypeToolRejected,
 		TypeToolAssessed,
 		TypeApprovalRequired, TypeApprovalResolved, TypeClarification,
+		TypeWorkflowProposed,
 		TypeWorkspaceBound, TypeArtifactCreated,
 		TypeArtifactValid, TypePlanLocked,
 		TypeRouterNarration: