feat(tui): event-derived ordering + retire Kotlin TUI

Rebuild the Go TUI transcript from the event stream instead of
optimistic local echoes. ChatTurnEvent now maps to ServerMessage.ChatTurn
(chat.turn); the TUI auto-vivifies sessions and renders user+router turns
from events. SessionStarted is de-special-cased into SessionAnnounced
(still carries workflowId), dropping the router.response shadow and
optimistic echoes.

Delete the unused Kotlin TUI (apps/tui) and add a kotlinx<->Go
golden-fixture test to lock the wire protocol. Gitignore server runtime
logs.

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

@@ -0,0 +1,86 @@
+package protocol
+
+import "testing"
+
+// Golden wire frames as emitted by the Kotlin server (kotlinx.serialization). These
+// strings are the cross-language contract: the Kotlin side pins the encode in
+// ServerMessageSerializationTest; this test pins the Go decode of the exact same bytes,
+// so a discriminator (@SerialName) or field-name drift fails loudly on one side.
+func TestDecodeGoldenServerFrames(t *testing.T) {
+	cases := []struct {
+		name      string
+		json      string
+		wantType  string
+		eventBear bool
+		check     func(t *testing.T, m ServerMessage)
+	}{
+		{
+			name:      "session.announced",
+			json:      `{"type":"session.announced","sessionId":"s1","workflowId":"healthcheck","sequence":6,"sessionSequence":1}`,
+			wantType:  TypeSessionAnnounced,
+			eventBear: true,
+			check: func(t *testing.T, m ServerMessage) {
+				if m.SessionID != "s1" || m.WorkflowID != "healthcheck" {
+					t.Fatalf("session.announced fields: %+v", m)
+				}
+			},
+		},
+		{
+			name:      "chat.turn",
+			json:      `{"type":"chat.turn","sessionId":"s1","turnId":"t9","role":"ROUTER","content":"hi there","sequence":7,"sessionSequence":2}`,
+			wantType:  TypeChatTurn,
+			eventBear: true,
+			check: func(t *testing.T, m ServerMessage) {
+				if m.Role != "ROUTER" || m.Content != "hi there" || m.TurnID != "t9" {
+					t.Fatalf("chat.turn fields: %+v", m)
+				}
+			},
+		},
+		{
+			name:      "stage.started",
+			json:      `{"type":"stage.started","sessionId":"s1","stageId":"write_script","occurredAt":123,"sequence":8,"sessionSequence":3}`,
+			wantType:  TypeStageStarted,
+			eventBear: true,
+			check: func(t *testing.T, m ServerMessage) {
+				if m.StageID != "write_script" {
+					t.Fatalf("stage.started fields: %+v", m)
+				}
+			},
+		},
+		{
+			name:      "tool.completed",
+			json:      `{"type":"tool.completed","sessionId":"s1","toolName":"shell","outputSummary":"ok","occurredAt":1,"diff":null,"sequence":9,"sessionSequence":4}`,
+			wantType:  TypeToolCompleted,
+			eventBear: true,
+			check: func(t *testing.T, m ServerMessage) {
+				if m.ToolName != "shell" || m.Summary != "ok" {
+					t.Fatalf("tool.completed fields: %+v", m)
+				}
+			},
+		},
+		{
+			name:      "snapshot_complete (non-event control frame)",
+			json:      `{"type":"snapshot_complete"}`,
+			wantType:  TypeSnapshotComplete,
+			eventBear: false,
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			m, err := Decode([]byte(c.json))
+			if err != nil {
+				t.Fatalf("decode failed: %v", err)
+			}
+			if m.Type != c.wantType {
+				t.Fatalf("type = %q, want %q", m.Type, c.wantType)
+			}
+			if m.IsEventBearing() != c.eventBear {
+				t.Fatalf("IsEventBearing = %v, want %v", m.IsEventBearing(), c.eventBear)
+			}
+			if c.check != nil {
+				c.check(t, m)
+			}
+		})
+	}
+}

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

@@ -1,7 +1,7 @@
 // Package protocol implements the correx WebSocket wire contract used to talk
 // to apps/server over /stream. The server (Kotlin/kotlinx.serialization) uses a
 // "type" class discriminator. Server->client variants carry @SerialName values
-// (e.g. "session.started"); client->server variants have no @SerialName, so the
+// (e.g. "session.announced"); client->server variants have no @SerialName, so the
 // discriminator is the fully-qualified Kotlin class name.
 package protocol
 
@@ -13,7 +13,8 @@ const clientPrefix = "com.correx.apps.server.protocol.ClientMessage."
 
 // Server message discriminator values (@SerialName on ServerMessage variants).
 const (
-	TypeSessionStarted   = "session.started"
+	TypeSessionAnnounced = "session.announced"
+	TypeChatTurn         = "chat.turn"
 	TypeSessionPaused    = "session.paused"
 	TypeSessionResumed   = "session.resumed"
 	TypeSessionCompleted = "session.completed"
@@ -54,6 +55,8 @@ type ServerMessage struct {
 	WorkflowID  string  `json:"workflowId"`
 	StageID     string  `json:"stageId"`
 	ToolName    string  `json:"toolName"`
+	Role        string  `json:"role"`
+	TurnID      string  `json:"turnId"`
 	Reason      string  `json:"reason"`
 	Summary     string  `json:"outputSummary"`
 	Response    string  `json:"responseText"`
@@ -168,7 +171,7 @@ func Decode(raw []byte) (ServerMessage, error) {
 // and are applied immediately.
 func (m ServerMessage) IsEventBearing() bool {
 	switch m.Type {
-	case TypeSessionStarted, TypeSessionPaused, TypeSessionResumed,
+	case TypeSessionAnnounced, TypeChatTurn, TypeSessionPaused, TypeSessionResumed,
 		TypeSessionCompleted, TypeSessionFailed,
 		TypeStageStarted, TypeStageCompleted, TypeStageFailed,
 		TypeInferenceStarted, TypeInferenceDone, TypeInferenceTimeout,