Fix Countdown

[kalverra]

Fixes a bug with human UI countdown till complete, makes it more dynamic.

[github-actions]

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[Copilot]

Pull request overview

This PR updates the human inline diagnose progress UI to show an ETA that counts down during in-flight iterations (serial and parallel), and improves parallel ETA accuracy by using completed iteration durations rather than pool wall time.

Changes:

• Add ETA helpers and adjust serial progress ETA to subtract in-flight elapsed time so the displayed “~X left” decreases each tick.
• Track and use the sum of completed iteration durations to compute a more representative average for parallel ETA.
• Update/extend unit tests for the new countdown behavior; bump related indirect Go module dependencies.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/runner/diagnose_progress.go	Implements countdown ETA logic and parallel duration-based averaging.
internal/runner/diagnose_progress_test.go	Updates expectations to validate countdown ETA behavior and adds coverage for parallel ETA with multiple actives.
go.mod	Updates indirect dependency version for charmtone.
go.sum	Syncs checksums for updated indirect dependencies.
tools/test/go.mod	Updates indirect tool-module dependency versions (ultraviolet, charmtone, go-runewidth).
tools/test/go.sum	Syncs tool-module checksums for updated indirect dependencies.

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