docs: add Topic Memory guide

[frf12]

Summary

Add a dedicated bilingual Topic Memory guide to the current documentation site.

Why

Topic Memory was described across the quickstart, configuration reference, and RFC, but it did not have a discoverable workflow page in the context-management sidebar. This change explains its lifecycle, configuration, verification flow, HTTP/MCP boundaries, prepared-context usage, and troubleshooting.

Related RFC: 1417 Topic Memory

Changes

• Add English and Simplified Chinese Topic Memory workflow pages.
• Add both pages to the Manage context sidebar and workflow index.
• Document the current HTTP contract, exact Artifact references, asynchronous flush semantics, and Topic Memory context assembly.

Validation

• make docs-test
• Link validation: 195 public pages and 264 repository files
• Static build and export verification: 794 public pages
• Commit hooks: JSON, formatting, Ruff, and ty checks passed

User-facing or breaking changes

Documentation only; no runtime or API behavior changes.

AI usage

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