perf: INP & Perceived Performance Audit — tracking issue

[macwilling]

Overview

Full audit of Interaction to Next Paint (INP) bottlenecks and perceived performance gaps across the codebase. Each sub-issue below is a self-contained PR targeting a specific problem area.

Sub-issues (recommended order)

• perf: replace window.confirm() with Dialog components #63 — Replace window.confirm() with Dialog components (P0 — blocks main thread)
• perf: add missing loading.tsx skeletons for data-heavy routes #64 — Add missing loading.tsx skeletons for data-heavy routes (P0 — blank page on navigation)
• perf: add optimistic updates for comment and attachment mutations #65 — Optimistic updates for comment and attachment mutations (P1 — dead silence after action)
• perf: add loading fallbacks to dynamic imports and auto-dismiss settings alerts #66 — Loading fallbacks for dynamic imports + auto-dismiss settings alerts (P1)
• perf: add confirmation dialogs to DeletePaymentButton and TimeEntryModal delete #67 — Confirmation dialogs for DeletePaymentButton and TimeEntryModal delete (P2)
• perf: replace "Loading…" text with skeleton in InvoiceBuilderClient time entries #68 — Replace "Loading…" text with skeleton in InvoiceBuilderClient (P2)

What was already good

• TaskStatusControl — uses useOptimistic + useTransition correctly ✅
• TaskTitleEditor — optimistic local state update before server call ✅
• DeleteTaskButton — correct Dialog confirmation pattern ✅
• CloseTaskDialog, TimeEntryModal save/edit — proper isPending label changes ✅
• tasks/loading.tsx, tasks/[taskKey]/loading.tsx — full structural skeletons ✅

Future development checklist

For all new features, check before opening a PR:

• Every destructive action uses Dialog, not window.confirm()
• Every button shows a label change while isPending (not just opacity)
• Every new route has a loading.tsx skeleton
• Every dynamic(..., { ssr: false }) has a loading prop
• List mutations (add/delete) use useOptimistic for instant feedback
• Client-side fetches show a skeleton, not a text string