test(sync): compare deepseek tui shadow parity

DeepSeek TUI is shadow-compared on this branch, so add the shared source-level proof that provider observation matches the existing ParseDeepSeekTUISession output. This keeps the branch review focused on an actual migration surface rather than only provider-local parser tests.

Validation: go fmt ./...; go test -tags "fts5" ./internal/parser ./internal/sync -count=1; go vet ./...; git diff --check; ./custom-gcl run --config .golangci.nilaway.yml ./internal/parser/... ./internal/sync/...

Author: mariusvniekerk

internal/sync/provider_shadow_deepseek_tui_test.go

@@ -0,0 +1,60 @@
+package sync
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.kenn.io/agentsview/internal/parser"
+)
+
+func TestObserveProviderSourceMatchesDeepSeekTUILegacyParser(t *testing.T) {
+	root := t.TempDir()
+	sourcePath := filepath.Join(root, "session_123.json")
+	writeProviderShadowSourceFile(t, sourcePath, deepSeekTUIShadowFixture())
+
+	provider, ok := parser.NewProvider(parser.AgentDeepSeekTUI, parser.ProviderConfig{
+		Roots:   []string{root},
+		Machine: "devbox",
+	})
+	require.True(t, ok)
+	sources, err := provider.Discover(context.Background())
+	require.NoError(t, err)
+	require.Len(t, sources, 1)
+
+	legacySession, legacyMessages, err := parser.ParseDeepSeekTUISession(sourcePath, "devbox")
+	require.NoError(t, err)
+	require.NotNil(t, legacySession)
+
+	observation, err := ObserveProviderSource(context.Background(), provider, ProviderObserveRequest{
+		Source:  sources[0],
+		Machine: "devbox",
+	})
+	require.NoError(t, err)
+	require.Len(t, observation.Results, 1)
+
+	assert.Equal(t, *legacySession, observation.Results[0].Session)
+	assert.Equal(t, legacyMessages, observation.Results[0].Messages)
+	assert.Equal(t, []string{legacySession.ID}, observation.Planned.DataVersionSessionIDs())
+	assert.Empty(t, observation.Planned.Diagnostics)
+}
+
+func deepSeekTUIShadowFixture() string {
+	return `{
+  "metadata": {
+    "id": "session_123",
+    "title": "Investigate DeepSeek TUI",
+    "created_at": "2026-06-01T10:00:00Z",
+    "updated_at": "2026-06-01T10:02:00Z",
+    "model": "deepseek-chat",
+    "workspace": "/Users/alice/code/sample-project"
+  },
+  "messages": [
+    {"role": "user", "content": "Inspect server logs", "timestamp": "2026-06-01T10:00:05Z"},
+    {"role": "assistant", "content": [{"type": "text", "text": "The server failed during startup."}], "timestamp": "2026-06-01T10:00:10Z"}
+  ]
+}`
+}