refactor: brand the command lifecycle pairing id as CommandId

commandId crosses three boundaries (session log, wire admission response,
client flow pairing), so per the branded-id rule it becomes
Branded<'CommandId'>, declared in a new pure @deepseek-ai/dsh-commands/brand
outlet (the dsh-llm/brand shape: type + constructor, no Context merges, so
wire and client programs can name it without loading the host plugin). The
event payloads, CommandExecution, and the executor mint carry the brand; the
wire schema gains commandIdSchema as the domain's single brand-cast point
(the approvals precedent); CommandNode and the fixture's fabrication cast
follow type-only.

packages/client/runtime/package.json

@@ -32,6 +32,7 @@
   "license": "BSD-3-Clause",
   "dependencies": {
     "@deepseek-ai/dsh-client-connection": "workspace:^",
+    "@deepseek-ai/dsh-commands": "workspace:^",
     "@deepseek-ai/dsh-client-ui-slots": "workspace:^",
     "@deepseek-ai/dsh-host-apiproxy": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",