Rename work item confidence to readiness in the UI

What does this MR do and why?

Renames the work item UI from Confidence to Readiness. This matches the existing readiness API and distinguishes it from security confidence assessments.

• Updates the visible label, accessible name, and help popover title.
• Updates the documentation and help anchor.
• Regenerates translations and updates affected expectations.

Part 2 of 3, targeting 628677-move-score-info-icon. The existing popover remains in use.

References

• #628677 (comment 3944896099)
• Drawer follow-up: !259135
• Depends on the icon placement: !259554 (merged)
• Related to #628677

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable workplan_score for a namespace with planning enabled.
2. Open a work item with a saved readiness score.
3. Verify the label is Readiness.
4. Hover or focus the information icon. Verify the title is What is the readiness score?
5. Follow Learn more to the readiness-score documentation section.

MR acceptance checklist

• Passed: 24 component tests and 14 workplan integration tests.
• Updated: documentation and translation catalog.
• Changelog: not required for this default-off feature.

Evaluate against the MR acceptance checklist.