feat(plugin): add namespaced hook API

[thdxr]

Summary

• replace the v2 Effect plugin host surface with namespaced hook and reload capabilities
• add Promise-based plugin definitions, adaptation, config discovery, and scoped reconciliation
• move runtime hooks into their owning domains and make internal plugin boot a discard layer

Validation

• bun typecheck in packages/core, packages/plugin, packages/server, and packages/opencode
• 283 affected core tests passed; the location-layer suite also passed independently after one contention timeout
• full repository Turbo typecheck passed in the pre-push hook

[greptile-apps]

Too many files changed for review. (143 files found, 100 file limit)