Release 0.1.5: update changelog and bump package versions

[Zhang-JiahangH]

Motivation

• Prepare and document the 0.1.5 release that introduces migration-friendly compatibility with react-diff-viewer props and several new diff/UI features.
• Signal package updates across workspace apps and the library so downstream consumers can pick up the new API and behavior.

Description

• Added a 0.1.5 entry to CHANGELOG.md describing new features like oldValue/newValue aliases, splitView toggle, unified (inline) diff rendering, renderContent(line) slot, line interaction APIs, codeFoldMessageRenderer, resetCodeBlocks() handle, expanded compareMethod options, and styling/theming enhancements.
• Bumped package versions from 0.1.4 to 0.1.5 in packages/react/package.json, apps/demo/package.json, and apps/benchmark/package.json to reflect the release.
• Updated workspace package references to use the new version where applicable without changing runtime code in this diff.

Testing

• No automated tests are configured or were executed as part of these changes; the modified packages do not include test scripts in the shown diffs.
• No typecheck or build commands were run in this rollout.

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Codex Task