Introduce workspace runtime and plugin platform

[AnlangA]

Summary

• introduce durable workspace runtime, persistence, migration, and shutdown flows
• add the plugin contracts, host, broker, repository, trust, manager, and sidecar integration
• update frontend application services, generated IPC contracts, quality gates, ADRs, and test coverage

Validation

• whitespace checks passed
• the local pre-commit quality gate is currently blocked by GHSA-jmr9-qjv8-65gv: the advisory requires extract-zip >=2.0.2, while npm currently publishes only 2.0.1
• GitHub checks remain authoritative for this PR