v0.9.0

Wire 0.4 / SDK 0.9.0

Breaking stdout vocabulary change (hard cutover from 0.3).

• Removed {"type":"session"} and {"type":"text"}
• Final body is a single {"type":"result","text":...} (optional usage)
• Session continuity is an optional session_id field on events (first non-empty persists)
• protocol_version is "0.4"

See CHANGELOG.md and Migration from 0.3.

Publishing to npm (agentproc@0.9.0) and PyPI is triggered by this tag via publish.yml.