Add measurable modernization task tracker

docs/modernization/roadmap.md

@@ -1,7 +1,7 @@
 # PanoPainter Modernization Roadmap
 
 Status: live
-Last updated: 2026-06-05
+Last updated: 2026-06-12
 
 This is the living roadmap for modernizing PanoPainter into independently
 testable C++23 components while retaining all existing functionality. Keep this
@@ -11,6 +11,9 @@ or temporary adapters live only in chat history.
 ## How To Keep This Roadmap Live
 
 - Update the phase status before and after each implementation pass.
+- Use `docs/modernization/tasks.md` for measurable execution tasks and
+  percentage/progress claims. The phase prose explains direction; the task
+  tracker is the source of truth for score changes.
 - When a shortcut is introduced, add it to the debt log section in this file
   until `docs/modernization/debt.md` exists, then move debt entries there.
 - When a major architectural decision is made, add an ADR under `docs/adr/`
@@ -51,6 +54,14 @@ or temporary adapters live only in chat history.
 | 7 | Hardening, Coverage, And Breaking-Point Tests | Not started | Each component has edge/failure tests |
 | 8 | Future Backend Readiness | Not started | Vulkan/Metal lab targets remain non-default |
 
+## Measurable Task Tracking
+
+Use `docs/modernization/tasks.md` before starting implementation work. It
+contains the current 100-point modernization scorecard, task states, ready
+queue, blocked queue, validation commands, and completion rules. Do not move the
+percentage for a narrowed adapter or added planner unless a task in that file is
+marked `Done` with validation and a debt/roadmap update.
+
 ## Target Component Architecture
 
 The refactor should move toward one-way dependencies: