fix: send displayName/mimeType in uploadToFileSearchStore body (fileSearchStores)

[daiki44]

Problem

When uploading a document to a File Search store via uploadToFileSearchStore using a Blob, the SDK does not send displayName (and related metadata) in the request body used to obtain the upload URL. As a result, created documents can end up with undefined and downstream retrieval/citations lose the friendly name.

Current Behavior

• config.displayName is accepted by the SDK call, but the value is not forwarded into the uploadToFileSearchStore request body.
• Documents created in File Search may show displayName: (no display name) even though the caller set it.
• This makes it hard to show friendly source names in RAG citations / grounding chunks.

Expected Behavior

• displayName provided in config should be persisted as the created document’s display name.
• mimeType provided in config should be forwarded consistently as part of the request metadata.
• SDK behavior should match the underlying File Search Stores API which supports these fields in the request body.

Fix

• Add displayName and mimeType to the JSON request body passed to the uploadToFileSearchStore endpoint when generating the upload URL.
• This aligns the SDK with the File Search Stores API request schema (which explicitly allows displayName and mimeType).

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