chore(release): prepare v0.2.3

[chaliy]

What

Prepare patch release v0.2.3 with version bump and changelog update.

Why

Release new features and fixes since v0.2.2.

How

• Bumped version in Cargo.toml from 0.2.2 to 0.2.3
• Updated CHANGELOG.md with v0.2.3 section including all changes since v0.2.2

Changelog excerpt

Highlights

• WebSocket mode for Responses API streaming
• OpenAI thinking/reasoning emulation support
• Fixed repository URLs for crates.io listing

What's Changed

• chore: routine maintenance - update deps and align specs (chore: routine maintenance - update deps and align specs #30)
• fix: correct repository URLs for crates.io listing (fix: correct repository URLs for crates.io listing #29)
• chore: add attribution settings and agent guidance for commits/PRs (chore: add attribution settings and agent guidance for commits/PRs #28)
• feat: add /ship command for full shipping workflow (feat: add /ship command for full shipping workflow #27)
• feat(api): add WebSocket mode for Responses API (feat(api): add WebSocket mode for Responses API #26)
• feat(api): add OpenAI thinking/reasoning emulation (feat(api): add OpenAI thinking/reasoning emulation #25)

Risk

• Low
• Standard version bump release

Checklist

• Tests added or updated
• Backward compatibility considered