fix(tui): align scrollbar position with viewport

[astkaasa]

Summary

• Add a shared TUI scrollbar state helper that maps list scroll offsets to Ratatui's full content-position range.
• Set viewport content length for scrollbars so thumbs reach the end of the track on the last visible page.
• Apply the helper across TUI list/detail scrollbars, including Overview and Hourly's effective data-row viewport.

Tests

• cargo test -p tokscale-cli scrollbar_state
• cargo test -p tokscale-cli test_overview_scroll_keeps_rendered_capacity_after_resize
• cargo test -p tokscale-cli

---

Summary by cubic

Fixes TUI scrollbars so the thumb matches the visible viewport across all screens and edge cases. The thumb now reaches the end of the track on the last page and stays at zero on single-page lists.

• Bug Fixes
  • Added a shared scrollbar helper to map scroll offsets to ratatui content positions, set viewport content length, and clamp overscroll using wide math for large lists.
  • Applied across Agents, Daily (table and detail), Hourly (uses data-row viewport), Minutely, Models, Overview top models, and Stats breakdown.

^{Written for commit 52ee94a. Summary will update on new commits.}

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
tokscale	Ignored	Preview	Jun 8, 2026 11:25pm

[cubic-dev-ai]

1 issue found

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[astkaasa]

unknown is the last item and is selected.

Left: my fix — the scrollbar is at the bottom.
Right: npx tokscale@latest — the scrollbar is in the middle.

[junhoyeo]

Reviewed: scrollbar rescaling math verified against ratatui 0.29 part_lengths(); all 8 ScrollbarState call sites consistent; cargo check/clippy/tests (709 passed incl. 5 new scrollbar tests) verified locally. Merging.

[junhoyeo]

@astkaasa cool, thanks a lot!