speed up flame graph TUI under heavy event load

Move the per-tick snapshot refresh off the Bubble Tea update goroutine,
add a frame ancestry index so navigation and filter helpers run in
O(subtree) instead of O(frames), skip refresh and animation while the
user is actively pressing keys, and memoize View() output. Keystrokes
(pause, filter, navigate) now land within one frame even when the live
trie ingests thousands of events per tick.

- new SnapshotTree() on LiveTrie bypasses JSON marshal+unmarshal
- RefreshFromLiveTrieCmd runs SnapshotTree + layout + ancestry on a
  background goroutine, coalesced via refreshInFlight, and returns a
  flameSnapshotReadyMsg the Update loop applies cheaply
- driveWindow gate (250 ms after last key press) skips refresh dispatch
  and snaps frames directly to target without animation while the user
  is driving
- View() caches its rendered string keyed on the inputs that affect
  output; cache is bypassed during animation

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/internal/flamegraph/livetrie_test.go b/internal/flamegraph/livetrie_test.go
index 5d4ce47..6a825c0 100644
--- a/internal/flamegraph/livetrie_test.go
+++ b/internal/flamegraph/livetrie_test.go
@@ -371,7 +371,7 @@ func TestLiveTrieConcurrentIngestAndSnapshot(t *testing.T) {
 		defer wg.Done()
 		for i := 0; i < 500; i++ {
 			payload, _ := lt.SnapshotJSON()
-			var snap trieSnapshot
+			var snap SnapshotNode
 			if err := json.Unmarshal(payload, &snap); err != nil {
 				t.Errorf("unmarshal snapshot: %v", err)
 				return
@@ -416,7 +416,7 @@ func TestLiveTrieStressHighRateConcurrentSnapshot(t *testing.T) {
 					return
 				case <-ticker.C:
 					payload, _ := lt.SnapshotJSON()
-					var snap trieSnapshot
+					var snap SnapshotNode
 					if err := json.Unmarshal(payload, &snap); err != nil {
 						errCh <- fmt.Errorf("snapshot json invalid: %w", err)
 						return
@@ -486,17 +486,17 @@ func newTestPair(comm string, pid uint32, tid uint32, path string, duration uint
 	return pair
 }
 
-func decodeLiveSnapshot(t *testing.T, lt *LiveTrie) trieSnapshot {
+func decodeLiveSnapshot(t *testing.T, lt *LiveTrie) SnapshotNode {
 	t.Helper()
 	payload, _ := lt.SnapshotJSON()
-	var snap trieSnapshot
+	var snap SnapshotNode
 	if err := json.Unmarshal(payload, &snap); err != nil {
 		t.Fatalf("unmarshal snapshot: %v", err)
 	}
 	return snap
 }
 
-func findSnapshotPath(t *testing.T, root *trieSnapshot, names ...string) *trieSnapshot {
+func findSnapshotPath(t *testing.T, root *SnapshotNode, names ...string) *SnapshotNode {
 	t.Helper()
 	node := root
 	for _, name := range names {
@@ -508,7 +508,7 @@ func findSnapshotPath(t *testing.T, root *trieSnapshot, names ...string) *trieSn
 	return node
 }
 
-func findSnapshotChild(node *trieSnapshot, name string) *trieSnapshot {
+func findSnapshotChild(node *SnapshotNode, name string) *SnapshotNode {
 	for _, child := range node.Children {
 		if child.Name == name {
 			return child