Prepare v0.3.0 release

[aaltshuler]

Summary

• Bump workspace crates from 0.2.2 → 0.3.0
• Add release notes at docs/releases/v0.3.0.md

Highlights

• --features aws + SecretsManagerTokenSource backend for the server
• Bearer auth hardening (SHA-256 hashed at rest, constant-time compare, server-authoritative actor id)
• GET /schema endpoint + CLI schema get command; static openapi.json with CI auto-sync
• Package workflow for CodeBuild-driven default + aws image builds
• Ephemeral __run__ branch hygiene (MR-670, MR-674)

Breaking

Repos created with 0.2.x that lack persisted schema state (_schema.pg, _schema.ir.json, __schema_state.json) or that have non-main public branches must be reinitialized before they can be opened with 0.3.0.

Test plan

• CI green
• Merging this tag (v0.3.0) triggers the release workflow and produces linux/macos artifacts + Homebrew tap update

🤖 Generated with Claude Code