Fixes #4887 - DimAuto.Calculate wrong height for vertical text before layout

[tig]

Summary

• Fix DimAuto.Calculate returning 0 for text height when TextFormatter.Direction is vertical and the view hasn't been laid out yet (Viewport.Width == 0)
• Add tests for GetAutoWidth() / GetAutoHeight() covering horizontal, vertical, with/without border
• Update AttributePicker to use GetAutoWidth() instead of GetWidthRequiredForSubViews() + GetAdornmentsThickness().Horizontal

Root Cause

In DimAuto.Calculate for Dimension.Height, when ConstrainToWidth is null the code uses Viewport.Width to constrain text width before measuring height. Before layout, Viewport.Width is 0, causing FormatAndGetSize(new Size(0, ...)) to return Height = 0 for any text — vertical or otherwise.

The fix uses the already-computed max-based width fallback (from line 190) when Viewport.Width is 0.

Test plan

• 8 new GetAutoWidth/GetAutoHeight tests (3 were failing before fix)
• All existing DimAutoTests pass
• Full parallelizable test suite: 15503 tests, 0 regressions

Fixes #4887

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes an edge case in DimAuto.Calculate where auto height could be computed as 0 for vertical text before the first layout pass (Viewport.Width == 0), and adds/uses new helper APIs to measure a view’s auto-sized dimensions.

Changes:

• Fix DimAuto.Calculate (height path) to avoid constraining text to width 0 before layout by falling back to the precomputed max-based width.
• Add View.GetAutoWidth() / View.GetAutoHeight() helpers and extend Dim.AutoTests with coverage for horizontal/vertical text and borders.
• Update AttributePicker to size _styleSelector via GetAutoWidth().

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
Terminal.Gui/ViewBase/Layout/DimAuto.cs	Fixes pre-layout text height measurement by avoiding a zero-width constraint.
Terminal.Gui/ViewBase/View.Content.cs	Adds GetAutoWidth() / GetAutoHeight() and refactors required-size helpers to use them.
Terminal.Gui/Views/Color/AttributePicker.cs	Switches style selector sizing to the new auto-size helper API.
Tests/UnitTestsParallelizable/ViewBase/Layout/Dim.AutoTests.cs	Adds test coverage for GetAutoWidth() / GetAutoHeight() including vertical text + border cases.