Add caller configuration to User-Agent header

[jhamon]

This PR adds support for capturing caller information (provider and model) in the Pinecone client configuration. The caller info is formatted and included in the User-Agent header for all requests, enabling telemetry about which AI agents/callers are using the SDK.

Changes

• Added optional caller property to PineconeConfiguration with structured object (provider?, model)
• Updated buildUserAgent to format caller info as caller=provider:model (with provider) or caller=model (without provider)
• Implemented normalization function similar to sourceTag handling
• Added comprehensive tests for caller formatting, normalization, and edge cases

Example Usage

const pc = new Pinecone({
  apiKey: 'your-api-key',
  caller: {
    provider: 'google',
    model: 'gemini'
  }
});
// User-Agent: ...; caller=google:gemini

---

Note

Adds support for embedding normalized caller info in request User-Agent and validates it via config.

• Introduces optional caller (provider?, model) to PineconeConfiguration and updates PineconeConfigurationProperties validation
• Extends buildUserAgent to append caller=provider:model or caller=model with normalization; adds formatCaller and normalizeCallerString (lowercase, trim, space->_, replace : with _, restrict charset)
• Updates tests: comprehensive user-agent specs for caller formatting, normalization, edge cases; adjusts constructor test error message to include caller in valid properties

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