fix: Improve usage reporting

[jsonbailey]

Note

Medium Risk
Primarily changes analytics/telemetry event names and adds constructor-time tracking; risk is moderate because it can break downstream metrics pipelines or increase event volume, but it does not alter core config evaluation logic.

Overview
Improves usage reporting in LDAIClientImpl by standardizing tracking event keys to $ld:ai:usage:* (e.g., completion-config, agent-config(s), judge-config, create-chat, create-judge) and ensuring createChat/createJudge don’t double-count config lookups by calling private _completionConfig/_judgeConfig helpers.

Adds an SDK initialization telemetry event ($ld:ai:sdk:info) emitted in the client constructor with { aiSdkName, aiSdkVersion, aiSdkLanguage }, and removes aiSdkName/aiSdkVersion from per-config tracker payloads (LDAIConfigTracker.getTrackData). Tests are updated accordingly, and sdkInfo now includes aiSdkLanguage.

^{Written by Cursor Bugbot for commit dad57a4. This will update automatically on new commits. Configure here.}

[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25462 bytes
Compressed size limit: 26000
Uncompressed size: 124854 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 171507 bytes
Compressed size limit: 200000
Uncompressed size: 799367 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 19742 bytes
Compressed size limit: 20000
Uncompressed size: 103795 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 23696 bytes
Compressed size limit: 25000
Uncompressed size: 82252 bytes

[joker23]

LGTM

[cursor]

Cursor Bugbot has reviewed your changes and found 4 potential issues.