feat(azure-cosmosdb): expose query request charges

[Saurish (nos-redacted)]

Summary

• add an optional callback that reports aggregated Cosmos DB request charges once per logical vector query
• support sync and async query pagination while preserving existing return values and document metadata
• expose a public immutable request-charge event and document the reporting contract
• raise the azure-cosmos minimum to 4.14.0, the first stable release without the stale initial query response hook

Testing

• 256 unit tests passed
• Ruff lint and format checks passed
• mypy passed across 50 files
• uv lock --check passed
• Cosmos authentication and Azure OpenAI embeddings were verified independently

Integration note

The credential-gated sync and async integration assertions are included. The complete live pytest case did not finish within the local VS Code terminal timeout, so this PR does not claim a successful end-to-end integration run.