Bump version from 0.2.9 to 0.3.0 across desktop/package.json,
tauri.conf.json, and Cargo.toml. Add v0.3.0 release notes covering
desktop long-session performance, streaming tool previews,
AskUserQuestion reliability, multi-client streaming, and H5 network
fixes.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
