Use Azure DocumentDB branding in vector search tutorial

[patty-chow]

Summary

Update docs/ai/vector-stores/tutorial-vector-search.md to use Azure DocumentDB, the current name of the managed service formerly called Azure Cosmos DB for MongoDB vCore.

• Update the article title, description, service references in prose, and one explanatory inline C# comment.
• Point the prerequisite to the Azure DocumentDB overview, using the repository's site-relative link convention. The previous /azure/cosmos-db/mongodb/ link points readers at the separate Azure Cosmos DB for MongoDB product.
• Describe the sample's upload destination as an Azure DocumentDB cluster rather than a Cosmos DB account.

Scope and preserved names

This is a one-article editorial correction, not a sample/API migration. Preserve the Cosmos Recipe Guide app name, exact UI option labels, sample repository URL, C#/CosmosDB-MongoDBvCore path, CosmosRecipeGuide.sln, VCoreMongoService.cs, MongoVcoreConnection, cosmosSearch, cosmosSearchOptions, and all executable code. The article's examples are inline fenced blocks, not linked snippet sources; only the service name in one non-executable comment changes. No RU-based Azure Cosmos DB product documentation, packages, model versions, or unrelated articles are changed.

Validation

• git diff --check — passed.
• npx --yes markdownlint-cli2@0.22.0 --config .markdownlint-cli2.jsonc docs/ai/vector-stores/tutorial-vector-search.md — passed, zero errors.
• Compared all nine fenced blocks with the base revision: identical except for the one branding-only comment; bold UI/solution text and the API cross-reference are unchanged.
• Confirmed the corrected prerequisite resolves successfully (HTTP 200) to the Azure DocumentDB overview and the existing referenced image is present in the repository.
• Reviewed remaining Cosmos/vCore references: all are intentional sample names, paths, UI strings, configuration keys, or query operators.
• No application build or Azure deployment was run: executable code and infrastructure are unchanged.

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Internal previews

File	Preview link
docs/ai/vector-stores/tutorial-vector-search.md	Learn preview

Build report

[patty-chow]

@dotnet-policy-service agree [company="{Microsoft}"]

[Copilot]

Copilot review overview

🟢 Approval recommended

The changes match the narrow editorial scope, preserve executable code, and have no unresolved findings.

Review effort: Balanced
Findings: None

What changed in this PR

Updates the vector-search tutorial to use Azure DocumentDB branding while preserving sample names, UI labels, and executable code.

Changes:

• Updates metadata, service references, and one explanatory code comment.
• Corrects the prerequisite link and describes the upload destination as a cluster.

File	Description
docs/​ai/​vector-stores/​tutorial-vector-search.md	Updates service branding, terminology, and the prerequisite link.

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[patty-chow]

@dotnet-policy-service agree

[patty-chow]

@dotnet-policy-service agree