extract dashboard tab framework into Tab registry for OCP compliance

Introduce tabDescriptor struct and tabDescriptors map in new
tabregistry.go. Each tab registers its name, short name, ordered
position, allowed viz modes, render function, scroll handler, and
optional init tick command. Adding a new tab now requires only a
single registry entry — no existing switch/if chains need editing.

Key changes:
- Tab.String() and tabLabel() use lookupTab() instead of a switch
- renderActiveTabContent() dispatches via d.Render (replaces renderActiveTab switch)
- handleScrollKey() dispatches via d.HandleScroll (replaces tab switch)
- Init() and postKeyTransitionCmd() use d.InitCmd (replaces stream/flame tab checks)
- allowedVizModes() delegates to tabAllowedVizModes() from registry
- orderedTabs() replaces hardcoded allTabs slice, derived from Position field
- bubbleChartFor() helper eliminates 5 repeated switch-on-tab for chart ops
- toggleBubbleMetric, tickActiveBubbleChart, moveBubbleSelection,
  activeBubbleChartHasNodes all use bubbleChartFor()
- refreshBubbleData split into two focused functions under 50 lines
- Two pre-existing test functions over 50 lines refactored

All tests pass; go build ./internal/tui/... clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 43 insertions, 32 deletions

diff --git a/internal/tui/dashboard/model_test.go b/internal/tui/dashboard/model_test.go
index a6c4455..4ca10c9 100644
--- a/internal/tui/dashboard/model_test.go
+++ b/internal/tui/dashboard/model_test.go
@@ -946,7 +946,10 @@ func TestPausedFlameDashboardViewPreservesZoomedSelectedLine(t *testing.T) {
 	}
 }
 
-func TestStreamPausedSupportsJKArrowsAndPageKeys(t *testing.T) {
+// newPausedStreamModel creates a stream tab model with 300 events, sized at
+// 120x30, and already paused — ready for scroll key assertions.
+func newPausedStreamModel(t *testing.T) Model {
+	t.Helper()
 	rb := eventstream.NewRingBuffer()
 	for i := 0; i < 300; i++ {
 		rb.Push(eventstream.StreamEvent{
@@ -958,21 +961,22 @@ func TestStreamPausedSupportsJKArrowsAndPageKeys(t *testing.T) {
 			FileName: fmt.Sprintf("/tmp/file-%03d", i),
 		})
 	}
-
 	m := NewModelWithConfig(nil, rb, 250, common.DefaultKeyMap())
 	m.activeTab = TabStream
 	m.showHelp = true
 	next, _ := m.Update(tea.WindowSizeMsg{Width: 120, Height: 30})
 	m = next.(Model)
-
 	m.streamModel.Refresh()
 	_ = m.View()
-
 	next, _ = m.Update(tea.KeyPressMsg{Code: tea.KeySpace}) // pause
-	m = next.(Model)
+	return next.(Model)
+}
+
+func TestStreamPausedSupportsJKArrowsAndPageKeys(t *testing.T) {
+	m := newPausedStreamModel(t)
 	before := rowFromStreamView(t, m.View().Content)
 
-	next, _ = m.Update(tea.KeyPressMsg{Code: []rune{'k'}[0], Text: string([]rune{'k'})})
+	next, _ := m.Update(tea.KeyPressMsg{Code: []rune{'k'}[0], Text: string([]rune{'k'})})
 	m = next.(Model)
 	afterK := rowFromStreamView(t, m.View().Content)
 	if afterK >= before {
@@ -1093,6 +1097,12 @@ func TestMetricToggleAppliesInFilesTreemapMode(t *testing.T) {
 	}
 }
 
+// pressKey sends a single rune key to model and returns the updated model.
+func pressKey(m Model, r rune) Model {
+	next, _ := m.Update(tea.KeyPressMsg{Code: r, Text: string(r)})
+	return next.(Model)
+}
+
 func TestFilesVisualizationRequiresDirectoryMode(t *testing.T) {
 	snap := statsengine.NewSnapshot(nil, nil, nil, nil, []statsengine.FileSnapshot{
 		{Path: "/tmp/a", Accesses: 3},
@@ -1102,45 +1112,43 @@ func TestFilesVisualizationRequiresDirectoryMode(t *testing.T) {
 	m.activeTab = TabFiles
 	m.latest = &snap
 
-	next, _ := m.Update(tea.KeyPressMsg{Code: []rune{'v'}[0], Text: string([]rune{'v'})})
-	model := next.(Model)
-	if got := model.filesVizMode; got != tabVizModeTable {
+	// v should not cycle viz mode when directory mode is off.
+	m = pressKey(m, 'v')
+	if got := m.filesVizMode; got != tabVizModeTable {
 		t.Fatalf("expected files treemap mode to stay disabled without directory mode")
 	}
 
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'d'}[0], Text: string([]rune{'d'})})
-	model = next.(Model)
-	if !model.filesDirGrouped {
+	// Enable directory mode; cycling should now work.
+	m = pressKey(m, 'd')
+	if !m.filesDirGrouped {
 		t.Fatalf("expected files dir mode enabled")
 	}
 
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'v'}[0], Text: string([]rune{'v'})})
-	model = next.(Model)
-	if got := model.filesVizMode; got != tabVizModeBubbles {
+	assertFilesVizCycle(t, m)
+}
+
+// assertFilesVizCycle verifies the full table→bubbles→treemap→icicle→table
+// cycle when directory mode is on, and that leaving dir mode resets to table.
+func assertFilesVizCycle(t *testing.T, m Model) {
+	t.Helper()
+	m = pressKey(m, 'v')
+	if got := m.filesVizMode; got != tabVizModeBubbles {
 		t.Fatalf("expected files bubbles mode enabled in directory mode")
 	}
-
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'v'}[0], Text: string([]rune{'v'})})
-	model = next.(Model)
-	if got := model.filesVizMode; got != tabVizModeTreemap {
+	m = pressKey(m, 'v')
+	if got := m.filesVizMode; got != tabVizModeTreemap {
 		t.Fatalf("expected files treemap mode enabled in directory mode")
 	}
-
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'v'}[0], Text: string([]rune{'v'})})
-	model = next.(Model)
-	if got := model.filesVizMode; got != tabVizModeIcicle {
+	m = pressKey(m, 'v')
+	if got := m.filesVizMode; got != tabVizModeIcicle {
 		t.Fatalf("expected files icicle mode enabled in directory mode")
 	}
-
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'v'}[0], Text: string([]rune{'v'})})
-	model = next.(Model)
-	if got := model.filesVizMode; got != tabVizModeTable {
+	m = pressKey(m, 'v')
+	if got := m.filesVizMode; got != tabVizModeTable {
 		t.Fatalf("expected files mode cycled back to table")
 	}
-
-	next, _ = model.Update(tea.KeyPressMsg{Code: []rune{'d'}[0], Text: string([]rune{'d'})})
-	model = next.(Model)
-	if got := model.filesVizMode; got != tabVizModeTable {
+	m = pressKey(m, 'd') // leave dir mode
+	if got := m.filesVizMode; got != tabVizModeTable {
 		t.Fatalf("expected files mode reset to table when leaving directory mode")
 	}
 }
@@ -1516,7 +1524,10 @@ func TestRenderActiveTabUsesDirectoryFilesViewWhenGrouped(t *testing.T) {
 		statsengine.HistogramSnapshot{},
 		statsengine.HistogramSnapshot{},
 	)
-	out := renderActiveTab(TabFiles, &snap, nil, nil, 120, 30, -1, 0, 0, 0, 0, true, 0, 0, 0, 0)
+	// Build a minimal model with dir-grouped mode enabled so the registry
+	// render function routes to the directory view.
+	m := Model{filesDirGrouped: true, pidFilter: -1}
+	out := renderActiveTabContent(&m, TabFiles, &snap, nil, nil, 120, 30)
 	if !strings.Contains(out, "Directory") {
 		t.Fatalf("expected grouped directory files view header, got %q", out)
 	}