- V2 tool execute hooks: add `ctx.tool.execute.before/after` plugin API,
core ToolHooks service, and registry wiring so hosted/local tool calls
run registered before/after hooks; provider-executed calls are excluded.
- Session synthetic endpoint: add `POST /api/session/:sessionID/synthetic`
with text/description/metadata plus regenerated Promise/Effect/JS client
surfaces.
- SessionInstructions service: read tool discovers nearby AGENTS.md walking
up to the Location root (exclusive) and injects them as durable synthetic
instructions, with lazy history dedup of prior claims.
- to-llm-message: stop forwarding synthetic message metadata to the model so
bookkeeping annotations stay model-hidden.
- schema changelog entry for synthetic metadata and the metadata leak fix.
Adds a plugin.list HTTP endpoint that reports currently loaded plugins, wires it through protocol, server, and generated clients, and merges it into sdk-next's plugin API. Also updates the sample plugin to register a primary agent instead of a subagent for local testing.
