feat(sdk): TypeScript SDK client + shared wire protocol + SDK subagent backend

- @deepseek-ai/dsh-sdk-protocol: extract the line transport from dsh-jsonrpc
  and name the request/result/notification wire types both ends share; error
  responses preserve wire code/data via JsonRpcResponseError.
- @deepseek-ai/dsh-sdk-client: TypeScript twin of the Python SDK — spawns the
  dsh-jsonrpc-agent runtime as a subprocess, drives stdio JSON-RPC turns
  (DeepSeekHarness high-level API + HarnessClient protocol client), scopes
  notifications to session trees client-side, and reaps the child through the
  shared subprocess dispose ladder.
- @deepseek-ai/dsh-subagent-sdk: out-of-process subagent backend driving a
  child harness runtime through the TS SDK; shares cwd resolution with
  subagent-acp via new dsh-subagent-subprocess cwd helpers.
- Keyless unit suites drive real subprocesses (scripted fake runtime peer);
  100% per-file coverage on all touched packages.

packages/ui/jsonrpc/src/index.ts

@@ -12,11 +12,10 @@
 import type { Context } from 'cordis'
 import type { Readable, Writable } from 'node:stream'
 import Schema from 'schemastery'
+import { JsonRpcLineTransport } from '@deepseek-ai/dsh-sdk-protocol'
 import { HarnessSdkServer } from './server.ts'
-import { JsonRpcLineTransport } from './transport.ts'
 
 export * from './server.ts'
-export * from './transport.ts'
 
 export const name = 'jsonrpc'
 // Only the agent factory is required; initialize reads the optional LLM seam with ctx.get().