chore: release v0.5.0

[tnez]

Summary

• bump @tnezdev/agentic from 0.4.1 to 0.5.0
• promote the Agentic migration changelog entry to the 0.5.0 release
• document public changes since 0.4.1: artifacts, workflow YAML/artifact contracts/version pinning, capabilities, lifecycle events, and release dogfood

Verification

• bun run typecheck
• bun test
• bash scripts/smoke-test.sh
• bash scripts/smoke-test-node.sh
• npm view @tnezdev/agentic@0.5.0 version --json returned E404 as expected before publish

Publish plan after merge

• sync main and confirm the merge commit is HEAD
• tag v0.5.0 and push the tag
• watch publish.yml complete via npm Trusted Publishing
• run bash scripts/post-publish-check.sh 0.5.0
• verify npm provenance badge for @tnezdev/agentic