fix(session-ui): show one count before used - #48038

Issue for this PR

Requested UI polish; no linked issue.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Changes grouped tool summaries from Used 1 Shell, 1 Read, 2 Agent to 4 used Shell, Read, Agent.

The overall count reflects calls, while tool names appear once in their original order. Uses lowercase used, keeps the copy localized, and updates the affected component and end-to-end expectations.

How did you verify your code works?

• Package typechecks and the repository's pre-push typecheck passed (35 tasks).
• 76 component tests passed, covering count updates, disclosure state, narrow/wide layouts, light/dark themes, and localized labels.
• One existing test fails before rendering: groups every collapsed tool until visible text separates the stack throws textVisible(...).get(...) is not a function. Reproduced the same error in an unchanged worktree at base commit 5c30292daa.
• Formatting and git diff --check passed.

Screenshots / recordings

Same production component and current-tool-group--mixed-tools Storybook fixture at 840 × 360, captured from the base commit and this branch.

Before	After

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR