fix : Chart widget axes render Unicode chars without ASCII fallback

[tmdeveloper007]

Summary of What Needs to be Done

The Chart widget (packages/widgets/src/data/Chart.ts) renders chart axes and Y-axis tick marks using hardcoded Unicode box-drawing characters (│, ─, └, ┤) without checking caps.unicode. This causes rendering issues in non-Unicode terminals.

Changes that Need to be Made

1. In packages/widgets/src/data/Chart.ts, add caps.unicode checks in _renderSelf() for the Y-axis line (│), X-axis line (─), origin corner (└), and Y-axis tick marks (┤).
2. Define ASCII fallback characters: | for vertical, - for horizontal, + for corners, and + for tick marks.
3. Add tests that verify chart axis rendering with ASCII fallback when caps.unicode is false.

Impact that it would Provide

Charts will render correctly with readable axes in any terminal environment, improving data visualization accessibility across different terminal types.

Note: Please assign this issue to the tmdeveloper007 account.

[github-actions]

✅ Auto-assigned to @tmdeveloper007 (issue opener).

Open your PR by 2026-08-10 (7 days). The bot frees this issue for another contributor after that date.

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