Tighten Google Drive file lifecycle skill

[Aismit]

Summary

Updates the Google Drive skill to make two Drive-native workflows explicit:

• Version-history comparison requests now route through grounding the file, fetching current content, listing revisions, fetching the immediately previous or requested revision, and comparing the two contents.
• File move requests now route through grounding the source file and target folder, reading parent metadata, using update_file with addParents and removeParents, preserving unrelated parents, and verifying the move.

Why

The 4/13 Hermes Google connector eval review had two easy, verifiable Drive failures that were not connector capability gaps:

• googledrive_read_007_compare_strategy_doc_to_previous_version failed because the assistant claimed prior versions were unsupported even though Drive revision tools exist.
• googledrive_write_008_move_file_to_target_folder failed because the assistant identified the file and destination but did not perform the parent update needed to move it.

These were skill/tool-selection misses, so the fix belongs in the Google Drive plugin skill rather than connector implementation.

Impact

This should make future Google Drive runs more likely to complete these workflows end to end instead of stopping early or incorrectly claiming unsupported capability.

Validation

• Ran git diff --check.
• Reviewed the final diff to confirm the change is limited to plugins/google-drive/skills/google-drive/SKILL.md.