fix(tui): fit project paths in open menu

[kitlangton]

What

Fit project paths within Open-menu rows without clipping the end of the already-truncated path, while using the full width of the large dialog on wider terminals.

This follows up on #39678. The path helper was given a width that did not match DialogSelect row geometry, and the original follow-up calculation still assumed a 60-column dialog although Open uses the 88-column large size.

Before / After

Before

A constrained 60-column row budgeted three columns more than it could display, so the path's final characters were clipped after truncation. On wider terminals, Open still capped the calculation at 60 columns and unnecessarily discarded up to 28 columns of its large dialog.

After

Dialog sizes and selectable-row content width have shared policies. Open calculates against its actual large-dialog width, constrained by the terminal, and truncateFilePath receives the exact remaining content width.

How

• packages/tui/src/ui/dialog.tsx owns medium, large, and xlarge dialog widths.
• packages/tui/src/ui/dialog-select.tsx owns the selectable-row content width.
• packages/tui/src/component/dialog-open.tsx derives path width from the large dialog and row content policies.
• packages/tui/src/component/dialog-move-session.tsx reuses the same row policy for its xlarge dialog.
• packages/tui/test/cli/tui/dialog-select.test.tsx covers constrained and full-width budgets and renders a truncated footer to verify its complete tail remains visible.

Scope

This does not change the path truncation algorithm or general dialog size values.

Testing

• cd packages/tui && bun run test (577 passed, 5 skipped)
• cd packages/tui && bun typecheck
• Pre-push hook: bun turbo typecheck --concurrency=3 (33 tasks passed)