chore(electron): add renderer implementation

[joker23]

This PR will add in the renderer implementation. There is an example of how this is used in https://github.com/launchdarkly/js-core/tree/skz/electron-sdk-next/packages/sdk/electron/example

with the change from initInRenderer -> createRendererClient.

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Note

Medium Risk
Touches cross-process IPC wiring and event subscription lifecycle/cleanup; failures could cause leaked ports/listeners or missing renderer updates, though coverage is strong and changes are largely additive.

Overview
Adds a full renderer-to-main IPC bridge for the Electron SDK. The main-process ElectronClient now registers ipcMain handlers for all flag/identify/flush/connection-mode APIs and supports renderer event subscriptions via MessagePort broadcasting, including cleanup on close() and a guard for add/remove ordering races.

Introduces the preload bridge (src/bridge) that exposes window.ldClientBridge and a new renderer client (createRendererClient / ElectronRendererClient) that delegates all calls over IPC and implements handle-based on()/off() subscription management with automatic teardown on close().

Includes small robustness/docs updates (safer ElectronDataManager start, typo fixes, updated IPC docs) and adds comprehensive Jest tests covering IPC calls, event subscription behavior, and resource cleanup.

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[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25394 bytes
Compressed size limit: 26000
Uncompressed size: 124693 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 23336 bytes
Compressed size limit: 25000
Uncompressed size: 81070 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: 798175 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 19331 bytes
Compressed size limit: 20000
Uncompressed size: 99578 bytes

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Cursor Bugbot has reviewed your changes and found 2 potential issues.