test(sdk): snapshot suite over the SDK path; docs for the SDK stack

- examples/jsonrpc-agent gains its first snapshot suite (sdk.snapshot.ts):
  the real dsh-jsonrpc-agent runtime driven through the real dsh-sdk-client,
  keyless llm-replay behind a new cordis.snapshot.yml overlay; three recorded
  scenarios (text turn, bash tool, spawn subagent) pin the notification
  stream, the SDK turn result, and the persisted parent+child session logs.
- Bilingual READMEs for dsh-sdk-protocol / dsh-sdk-client / dsh-subagent-sdk;
  sdk/ and subagent/ group tables extended; dsh-jsonrpc README points at the
  extracted protocol package; Agent Note (en+zh) owns the decision.
- The proposed make-jsonrpc-directional note is updated for the transport's
  new home and its second (client) consumer.
- Model Experience sentence allowlist entries for the two client-side
  packages; module graph + config catalog regenerated; i18n pairings
  recorded. doc-sync passes 24/24.

examples/jsonrpc-agent/cordis.yml

@@ -38,6 +38,8 @@
   name: '@deepseek-ai/dsh-session-persistence-jsonl'
   config:
     root: !!js process.env.DSH_SESSION_ROOT ?? './.sessions'
+    # Snapshot runs read the raw JSONL back; production keeps zstd frames.
+    compression: !!js "process.env.DSH_SNAPSHOT === undefined ? 'zstd' : 'none'"
 
 - id: session-checkpoints
   name: '@deepseek-ai/dsh-session-checkpoint-policy'