Show the window around the current position in GetChangeVisualizations

[matt-edmondson]

Fixes #96

What changed

GetChangeVisualizations(maxItems) used to return commands.Take(maxItems), which is the oldest commands. With 60 commands and the default limit of 50, a history panel never showed the current command c59 or the 9 commands before it.

It now picks which commands to return like this:

• Default: the most recent maxItems commands.
• Current position undone to before that window: the window is centred on the current position, so it holds the current command and the redoable commands after it.

Position is still the absolute stack index, so IsExecuted and HasSaveBoundary stay correct for the shifted window. A maxItems of zero or less returns no items.

The result is now a list rather than a lazy query over the live stack. This fixes the GetChangeVisualizations half of #95. The GetCommandsToUndo half of #95 is left for its own PR.

The XML doc on IUndoRedoService.GetChangeVisualizations and docs/api-reference.md now describe which window is returned.

Tests

New tests in UndoRedoStackTests:

• 60 commands with a limit of 50 returns c10..c59, ending at Position == 59.
• After 5 undos, the current command (54) is marked executed, and the 5 redoable commands are included and marked not executed.
• After 40 undos with a limit of 10, the window contains position 19 and some redoable commands, and positions are absolute.
• A save boundary inside a shifted window is reported at its absolute position.
• A limit of zero or a negative limit returns an empty result. This passed before the change too; the test guards the explicit handling.

The first four failed on main. The full suite passes with the change (75/75).

🤖 Generated with Claude Code

https://claude.ai/code/session_01N4m2HJkrsY88XBtTqTKAkE

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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