Add error checking for file I/O operations in ReportCommand

[Copilot]

Addresses feedback from PR #10 review: file operations (mkdir, copy, file_put_contents) lacked failure checks, causing silent failures or generic PHP warnings on permission/disk space issues.

Changes:

• Wrap all file I/O operations in error checks that throw RuntimeException on failure
• Include file path and common failure causes (permissions, disk space) in error messages
• Applied to: directory creation, report.js/chart.js/styles.css/index.html writes, and asset copies

Example:

// Before
file_put_contents($destination, 'const reportData = '.$json.';');

// After
if (false === file_put_contents($destination, 'const reportData = '.$json.';')) {
    throw new \RuntimeException(sprintf('Failed to write report data to "%s". Check permissions and disk space.', $destination));
}

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[makomweb]

Please close this one. I have applied changes manually due to other changes making it less necessary to apply these changes.

[Copilot]

Please close this one. I have applied changes manually due to other changes making it less necessary to apply these changes.

Understood. This PR can be closed as you've applied the changes manually.