Add missing 'assistant' option to contextual menu docs

[mintlify]

Summary

• Added the missing assistant option to the contextual menu options list in the settings reference documentation

This option was already documented in the contextual menu page but was missing from the comprehensive settings reference, which lists all available options.

Triggered by: Package bump commit mintlify/mint@559a18a for @mintlify/client@0.0.2635

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Note

Low Risk
Low risk documentation-only change; no runtime behavior or configuration parsing is modified.

Overview
Adds the missing "assistant" entry to the contextual.options enum in organize/settings.mdx, including a short description of what the option does, so the global docs.json settings reference matches the supported contextual menu actions.

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