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/web/control-page.ts

@@ -1,4 +1,4 @@
-import type { OpenClawPluginApi } from "openclaw/plugin-sdk";
+import type { OpenClawPluginApi } from "openclaw/plugin-sdk/core";
 import type { ChannelStore, ChannelMode } from "../core/channel-store.js";
 import type { IdentityRegistry } from "../core/identity-registry.js";
 import { fetchAdminGuilds, fetchGuildChannels } from "../core/moderator-discord.js";

plugin/web/dirigent-api.ts

@@ -1,4 +1,4 @@
-import type { OpenClawPluginApi } from "openclaw/plugin-sdk";
+import type { OpenClawPluginApi } from "openclaw/plugin-sdk/core";
 import type { ChannelStore } from "../core/channel-store.js";
 
 type Deps = {