Inspector: scope stats and call tree to the selected timeline range

[lukecotter]

Summary

When a range is selected or zoomed on the Timeline, the Inspector's no-selection content — log overview, time-by-category, hot spots and the call tree — should recompute for just that window.

Today the Inspector is either empty or whole-log, so narrowing the timeline to a suspicious 3 seconds tells you nothing about what is inside it. Chrome DevTools' Performance panel behaves the way we want: its Summary and Bottom-Up tabs describe the selected range, falling back to the whole profile when nothing is selected.

Behaviour

• Selecting or zooming to a range on the Timeline re-scopes the Inspector's default content to that window.
• Clearing the range returns it to whole-log figures.
• Figures must be labelled as range-scoped. A user glancing at "SOQL 12" needs to know instantly whether that is the transaction or the window — an unlabelled number here is worse than no number.
• A selected frame still wins: an explicit selection shows that frame, not the range.

Constraints worth recording

• It re-aggregates on every viewport change, so it needs debouncing and a stated perf budget. The renderer's own budget is 60fps on 500k+ line logs; the re-aggregation must not be what breaks it.
• The call tree needs pruning to the range rather than rebuilding from scratch, for the same reason.
• Depends on the Inspector's default/no-selection states landing first — the range view is a filtered version of exactly that content, so building it beforehand means building it twice.

Related

• feat: interactive calltree on timeline #113 — the Inspector itself.