PR_26179_CHARLIE_030-sprites-undo-redo

[ToolboxAid]

Summary

• Add Undo and Redo controls for Sprite Creator page-session editor actions.
• Cover pencil, eraser, fill, clear canvas, and reset actions.
• Keep all state unsaved and non-authoritative.

Validation

• PASS: node --check assets/toolbox/sprites/js/index.js
• PASS: node --check dev/tests/playwright/tools/SpritesToolShell.spec.mjs
• PASS: git diff --check for touched runtime/test files
• PASS: targeted Sprite Creator Playwright shell test

Artifact

• dev/workspace/zip/PR_26179_CHARLIE_030-sprites-undo-redo_delta.zip

[chatgpt-codex-connector]

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Reviewed commit: 4f85c454b6

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[chatgpt-codex-connector]

Avoid recording no-op resets

When the draft is already an empty 16x16 canvas, such as immediately after undoing a paint from the initial grid, clicking Reset to 16x16 makes no visible state change but this unconditional history push clears the redo stack via pushUndoSnapshot(). That disables Redo and loses the user's ability to restore the undone edit, so the reset should only record history when the grid size or painted pixels would actually change.

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