docs: Document Inception Labs mercury-2 model and capabilities

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Summary

PR #12156 added support for Inception Labs mercury-2 model with 128k context and tool calling capabilities. The Inception provider documentation at /docs/customize/model-providers/top-level/inception.mdx needs to be updated to:

• Document the mercury-2 model specifically
• Mention the 128k context length
• Document tool calling support
• Add mercury-edit-2 and mercury-coder-small models

Related PR

• feat: add Inception Labs mercury-2 model #12156 (feat: add Inception Labs mercury-2 model)

Documentation Location

• /docs/customize/model-providers/top-level/inception.mdx