fix: don't block one-shot openclaw subcommands; migrate to current plugin SDK

Sidecar lifecycle:
- Move startSideCar() out of register() into an api.on("gateway_start", ...)
  handler. register() runs in every CLI subprocess that loads plugins
  (e.g. `openclaw completion`, `openclaw doctor`); eagerly spawning a
  long-lived process there hung `openclaw update`'s post-update steps.
- Spawn the sidecar with detached: true, stdio routed to a log file fd,
  and call .unref() so the host's event loop is never held by the child.
  Even if a future caller invokes startSideCar in a non-gateway context,
  it can no longer block that host from exiting.
- Sidecar logs now go to ~/.openclaw/logs/dirigent-sidecar.log instead of
  being piped through the host logger.

Plugin SDK convention update:
- Wrap default export with definePluginEntry({ id, name, description, register })
  per the current openclaw plugin authoring contract.
- Switch all imports from the deprecated root barrel "openclaw/plugin-sdk"
  to focused subpaths "openclaw/plugin-sdk/core" and
  "openclaw/plugin-sdk/plugin-entry".
- Modernize openclaw.plugin.json: drop entry/version, add description,
  declare contracts.tools[] for the 6 tools, set activation.onStartup: true
  so gateway_start fires for this plugin at boot.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugin/openclaw.plugin.json

@@ -1,9 +1,20 @@
 {
   "id": "dirigent",
   "name": "Dirigent",
-  "version": "0.3.0",
   "description": "Rule-based no-reply gate with provider/model override and turn management",
-  "entry": "./index.ts",
+  "activation": {
+    "onStartup": true
+  },
+  "contracts": {
+    "tools": [
+      "dirigent-register",
+      "create-chat-channel",
+      "create-report-channel",
+      "create-work-channel",
+      "create-discussion-channel",
+      "discussion-complete"
+    ]
+  },
   "configSchema": {
     "type": "object",
     "additionalProperties": false,