refactor(storage): improve LocalTempFileTrait docs and harden toTmpFile stream handling

[joshtrichards]

• Resolves: #

Summary

• Replaces inherited/outdated trait docblock text with trait-specific documentation.
  • Existing docblock was just a copy/paste of the one from Common and thus was not adding anything and was inaccurate.
• Adds focused method-level docblocks
• Refactors toTmpFile() for robustness and readability:
  • use pathinfo(..., PATHINFO_EXTENSION) for clearer/consistent extension extraction
  • handle target fopen failure explicitly
  • ensure both source and target streams are always closed via try/finally

TODO

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI