Release: weavegraph v0.4.0 — Final API Freeze

[Idleness76]

Summary

v0.4.0 is the final API freeze release. No new features — only removals, renames, and documentation finalization. The public API surface is now locked for v1.0.

Milestones

• 0.4.1 — Removed all deprecated items from 0.2.0/0.3.0: Message::new(), RuntimeConfig.checkpointer field + with_checkpointer() + checkpointer_type(), six legacy AppRunner constructors, LadderError type alias
• 0.4.2 — Removed llm = ["rig"] feature alias; rig is now the sole name
• 0.4.3 — Added DIAGNOSTIC_SCOPE const alongside STREAM_END_SCOPE
• 0.4.4 — Added examples/production_streaming.rs: full Axum + SSE + Postgres checkpointing reference, end-to-end tested against live Postgres

Additional

• cargo deny check clean (aws-lc-sys updated 0.38→0.40 to clear 6 security advisories)
• cargo semver-checks clean against 0.3.0 baseline
• docs/MIGRATION.md v0.4.0 section added (6 breaking changes with before/after examples)
• CHANGELOG.md [0.4.0] entry added

Checklist

• cargo check --all-features clean
• cargo test --all-features passes (non-postgres)
• cargo test --doc --all-features — 155 passed, 0 failed
• cargo doc --all-features --no-deps — 0 warnings
• cargo deny check clean
• cargo semver-checks check-release --baseline-version 0.3.0 clean