## Overview
Split from #26466, scoped to **agent-only** changes. This PR exposes the
agent's context sources and snapshots over the existing agent socket.
There
are no changes outside `agent/`.
## What's included
- **agentsocket**: context source CRUD (`ContextSources`,
`GetContextSource`,
`AddContextSource`, `RemoveContextSource`) plus `GetContextSnapshot` and
`ResyncContext` RPCs, with matching client methods and proto. The server
receives the context `Manager` via `WithContextManager` and returns a
clean
error when it is absent.
- **agentcontext**: the resync JSON response now carries the
per-resource
`Name`, keeping the HTTP resync payload in sync with the drpc
`PushContextState` path in `agentsocket`.
- **agent**: passes the context `Manager` to the socket server via
`WithContextManager`.
## What's intentionally NOT here
- No MCP wiring. There are no MCP additions in `agent.go` or
`agentcontext`.
MCP ownership will land later in `agentcontext`; this PR does not build
on
`agent/x/agentmcp`.
- No changes to `agent/x/agentmcp` or the `agentcontext` resolver. The
socket
serves whatever context resources the `Manager` already resolves.
<details>
<summary>Context for reviewers</summary>
This is one of several PRs split out of #26466. Earlier revisions also
wired
live MCP servers through the socket; that scope was removed so this PR
stays
purely socket + context plumbing inside `agent/`. The agentcontext
resolver,
`agent/x/agentmcp`, and `agent.go` MCP startup behavior are unchanged
from
`main`.
</details>
---
_Created by Coder Agents on behalf of @kylecarbs._
