feat(planning): follow the indicative wait in calculation progress

The overlay percentage now rises linearly to 95% at the expected wait
captured at Calculate, holds there, and shows 100% only when the planner
completes. Beneath the status, one line names the current planning stage
(with the rule name for rule stages) and another shows the approximate
remaining time, or "Taking longer than expected" once the wait is
exceeded, announced once through the live status. Cancel freezes the
percentage and hides both lines.

PlanningCalculationService reports the stage and submitted request
instead of fixed per-stage percentages; PlanningDurationService owns the
wait progress on a 250 ms tick.

Closes #300

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/planning-duration.md

@@ -82,6 +82,25 @@ duration rounding to whole milliseconds prevents floating-point noise at unit
 boundaries. Very fast runs can finish before the displayed lower bound. The
 range is explicitly indicative, not a confidence interval or a promise.
 
+## During a calculation
+
+The loading overlay's percentage follows the indicative wait, not the planning
+stages completed. At Calculate, `PlanningDurationService` freezes the expected
+duration `e` for the submitted snapshot, including the local refinement. On a
+250 ms tick, it measures elapsed time from the same timestamp the calibration
+uses. Progress rises linearly to 95% at `e`, holds there and shows 100% only
+when the planner reports completion. Per-stage weights are not used, because
+the costly stage depends on the configuration. Form edits and repeated stages
+cannot move it backwards. On Cancel, the tick stops and the percentage freezes.
+
+Below the status, one line names the current planning stage. For an
+optimization or preference stage, it shows the rule's name. When `e` is at least
+3 seconds, a second line shows "About N s left". This is in whole seconds under
+10 seconds, 5-second steps under a minute and whole minutes after that. Once
+the elapsed time reaches `e`, the line reads "Taking longer than expected" for
+any `e`, and the live status announces it once. Both lines are visible text,
+not live regions, and are hidden after Cancel.
+
 ## What is timed
 
 Every request, manual or initial, captures `performance.now()` inside