docs: Clarify Naming Consistency in Section 1.2

[mdqst]

Motivation

While reviewing the documentation, I noticed a potential source of confusion in Section 1.2. The title refers to "Id Gateway," but within the section itself, the term "IdManager" is used repeatedly.

To ensure consistency and clarity for readers, I've updated the section title in the Table of Contents and throughout the document to "IdManager," as this term seems to reflect the intended name.

Merge Checklist

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PR-Codex overview

This PR focuses on updating the documentation in docs/docs.md to correct the naming of a section related to the ID management system.

Detailed summary

• Changed the section title from [Id Gateway](#12-id-manager) to [Id Manager](#12-id-manager) in the documentation.

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