Use compact token counts in session information

[SmartAI]

Summary

• Abbreviate token counts with k, M, and B across session information without changing the layout.
• Preserve exact counts in tooltips and accessibility labels.
• Cover compact formatting and rounded unit boundaries in the desktop regression test.

Validation

• Focused desktop and analytics tests: 17 passed, 1 skipped.
• Ruff and git diff checks passed.