chore: release packages 0.9.0 - #120

Summary

Release the changes already merged into main as OpenAgentPack 0.9.0. Bump SDK, CLI, and Playground together, update their changelogs, and consume the eight pending changesets.

Behavior / risk

• The private server package advances from 0.0.14 to 0.0.15 due to the SDK dependency update.
• The lockfile changes only the four workspace version fields; dependency resolutions and runtime code are unchanged.
• Merging this release PR into main triggers the stable npm publishing workflow when NPM_RELEASE_ENABLED is enabled.

Validation

• Normal pre-push verification passed: all workspace type checks, architecture checks, all 1,658 tests, and changed-file lint.
• All 11 release channel, snapshot, and publish tests passed.
• Package versions, changelog versions, and lockfile versions agree; CLI reports 0.9.0.
• Git diff whitespace checks passed.