fix(core-tools): show ellipsis on multi-line edit snippets

[mc856]

Summary

EditToolInvocation.getDescription() decided whether to append ... to the
snippet by checking the full string length. For multi-line edits whose first
line was short (≤ 30 chars), the ellipsis was skipped and the confirmation UI
looked like only a single short line changed.

New condition: firstLine.length > 30 || s.includes('\n') — ellipsis appears
whenever the snippet actually hides content from the user. CRLF handling is
unchanged from the original implementation.

Related Issues

Fixes #28110
Fixes #28109

How to Validate

npx vitest run packages/core/src/tools/edit.test.ts -t "getDescription"
# 8 passed — includes a regression case for the issue, boundary cases
# (exact 30 chars, empty new_string), and the no-change / Create paths.

Drive-by: also canonicalizes the test's tempDir via fs.realpathSync so
edit.test.ts runs cleanly on macOS (previously ~30 unrelated cases in the
same file failed locally due to /var → /private/var).

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a display issue in the edit tool's confirmation UI where multi-line snippets were incorrectly presented without an ellipsis if the first line was short. The changes ensure that users are properly notified of hidden content in multi-line edits. Additionally, the PR improves test suite stability across different operating systems and removes legacy bot configuration files that are no longer in use.

Highlights

• Ellipsis Logic Fix: Updated the snippet generation logic in EditToolInvocation to ensure an ellipsis is displayed whenever a snippet contains multiple lines, regardless of the first line's length.
• Regression Testing: Added comprehensive unit tests for the getDescription method to cover boundary conditions and multi-line edit scenarios, addressing issues Bug: EditTool getDescription snippet doesn't show ellipsis for multi-line edits with short first lines #28110 and Bug: EditTool description snippet incorrectly truncates multi-line strings #28109.
• Test Environment Stability: Improved test reliability on macOS by canonicalizing the temporary directory path using fs.realpathSync, preventing path resolution failures.
• Cleanup: Removed obsolete Gemini CLI bot agent and skill configuration files from the repository.

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[github-actions]

📊 PR Size: size/M

• Lines changed: 131
• Additions: +124
• Deletions: -7
• Files changed: 2

[gemini-code-assist]

Code Review

This pull request refactors the description snippet generation in EditTool to correctly append an ellipsis when content is hidden, adds comprehensive unit tests for these scenarios, and canonicalizes the temporary directory path in tests to resolve macOS path mismatches. It also removes several obsolete agent/skill definition files. The reviewer recommended handling CRLF line endings to prevent terminal rendering corruption and using Array.from() to avoid splitting multi-byte Unicode characters during truncation.

[gemini-code-assist]

When splitting the string by \n on files with CRLF (\r\n) line endings, the resulting firstLine will retain the trailing carriage return (\r). Since this is a terminal-first CLI tool, printing a string containing a carriage return followed by an ellipsis (e.g., foo\r...) can cause the terminal cursor to reset to the beginning of the line, leading to rendering corruption where the ellipsis overwrites the start of the line.

Additionally, when truncating strings that may contain multi-byte Unicode characters (such as emojis), we should use methods that operate on grapheme clusters (like Array.from()) instead of UTF-16 code units (string.length, string.substring()) to prevent character splitting.

Suggested change

	const snippet = (s: string) => {
	const firstLine = s.split('\n')[0];
	const hasHiddenContent = firstLine.length > 30 || s.includes('\n');
	return firstLine.substring(0, 30) + (hasHiddenContent ? '...' : '');
	};
	const snippet = (s: string) => {
	const firstLine = s.split(/\r?\n/)[0];
	const chars = Array.from(firstLine);
	const hasHiddenContent = chars.length > 30 || s.includes('\n');
	return chars.slice(0, 30).join('') + (hasHiddenContent ? '...' : '');
	};

References

1. When truncating strings that may contain multi-byte Unicode characters (e.g., emojis), use methods that operate on grapheme clusters (like Intl.Segmenter or Array.from()) instead of UTF-16 code units (string.length, string.slice()) to prevent character splitting.

[github-actions]

🛑 Action Required: Evaluation Approval

Steering changes have been detected in this PR. To prevent regressions, a maintainer must approve the evaluation run before this PR can be merged.

Maintainers:

1. Go to the Workflow Run Summary.
2. Click the yellow 'Review deployments' button.
3. Select the 'eval-gate' environment and click 'Approve'.

Once approved, the evaluation results will be posted here automatically.

[mc856]

Force-pushed to remove an unintended 5-file deletion under tools/gemini-cli-bot/.gemini/ — those files were missing from my local snapshot of upstream (the directory is matched by the repo's **/.gemini/ gitignore, but the files were tracked before that rule was added). Restored them verbatim from upstream and re-pushed. The PR now only contains the intended edit.ts + edit.test.ts changes (+124/-7).