Getting Gradial to do what you want.

Gradial reads finished runs from Apple Health, so the run has to be in Health first. Check Settings, Privacy & Security, Health, Gradial and confirm that Workouts, Workout Routes and Heart Rate are on. iOS only asks for permission once, so if you declined the first time, this is where you change it.

A run is matched to the session it most plausibly satisfied, on date and distance. A run three days from the planned day, or less than about two thirds of the distance asked for, will not be matched. You can look at any week to see which sessions were matched and which were not.

Predictions are built from Apple Health's VO₂max, which Health only writes after a few outdoor runs with heart rate on an Apple Watch. Until it has one, Gradial predicts from the race time you entered when you built the plan, and says so rather than showing a confident number it cannot support.

Scheduling needs a paired Apple Watch on watchOS 26 or later, and the first send asks the watch for permission. If no watch is paired the button says so. Sessions appear in the Workout app on the watch on the day they are scheduled.

Two levers. On the Plan tab, the fitness check offers to re-anchor the whole plan to your measured fitness. Inside it, Adjust this plan lets you nudge every pace or the weekly volume by a percentage, or schedule a time trial and anchor to the result.

Settings, Privacy & Security, Health, Gradial, and turn off whatever you want to withhold. The app keeps working and says which parts have gone quiet. To remove everything Gradial has stored, delete the app: the plan file goes with it, and your Health data was never copied out in the first place.

Not directly. Nothing leaves the phone, which also means nothing syncs to a second one. Your runs live in Apple Health and travel as Health travels; the plan itself does not, and you would build it again.