chore: update provider examples to use createTracker() factory

[jsonbailey]

Summary

• Updates JSDoc @example blocks and README code snippets in the LangChain, OpenAI, and Vercel AI provider packages to use the new config.createTracker() factory pattern introduced in @launchdarkly/server-sdk-ai v0.17.0
• Removes references to the removed config.tracker property across 3 READMEs and 2 source files

Test plan

• Verify no remaining aiConfig.tracker or config.tracker property accesses in the provider packages
• Confirm JSDoc examples compile and reflect the current API

🤖 Generated with Claude Code

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Note

Low Risk
Low risk because this is documentation/JSDoc example updates only, aligning sample code with the newer tracking API without changing runtime provider behavior.

Overview
Updates LangChain, OpenAI, and Vercel provider READMEs and JSDoc examples to use the aiConfig.createTracker() factory, replacing direct aiConfig.tracker property access.

This keeps the sample tracking calls (trackMetricsOf/trackStreamMetricsOf) the same but ensures examples match @launchdarkly/server-sdk-ai v0.17.0’s API.

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[github-actions]

@launchdarkly/js-sdk-common size report
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Compressed size: 25623 bytes
Compressed size limit: 29000
Uncompressed size: 125843 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 31700 bytes
Compressed size limit: 34000
Uncompressed size: 113136 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 179470 bytes
Compressed size limit: 200000
Uncompressed size: 830325 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 37607 bytes
Compressed size limit: 38000
Uncompressed size: 207149 bytes