fix: resolve -o option conflict between global output and filesystem output-format

[haosenwang1018]

Closes #219

The -o short flag is used for both the global --output option (json/table) and the filesystem --output-format option (agent/original), causing conflicts when used together (e.g. ov ls -o original).

This fix changes the filesystem --output-format short flag from -o to -f, resolving the ambiguity. Users can now use:

• -o json / -o table for global output format
• -f agent / -f original for filesystem content format

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