feat: integrate AgentRQ task manager plugin

- Clone agentrq/agentrq plugin to plugins/agentrq/
- Update package.json name to 'agentrq'
- Add agentrq plugin to tauri.conf.json resources
- Add AGENTRQ_PACKAGE constant and bundled_agentrq_plugin() discovery
- Add install_agentrq_plugin() function to modlens.rs
- Update README with plugin listing

plugins/agentrq/cordis.patch.yml

@@ -0,0 +1,18 @@
+# The @agentrq/dsh-plugin-agentrq bundle patch. Applied when a profile lists
+# this bundle, over whatever earlier layers (normally @deepseek-ai/dsh-base)
+# already contributed.
+#
+# One row, one endpoint. The plugin mounts @deepseek-ai/dsh-mcp-client itself as
+# a child fiber, so the workspace URL is configured once and the bridge shares
+# this row's lifetime. Everything else has a schema default.
+#
+# `url` falls back to AGENTRQ_WORKSPACE_MCP_URL, which suits a container or CI
+# job. For an interactive install, pin the endpoint in the profile's own
+# cordis.patch.yml instead: that layer is applied after this one, and dsh
+# watches it, so an edit takes effect without a restart.
+
+- insert:
+    - id: agentrq
+      name: 'agentrq'
+      config:
+        url: !!js process.env.AGENTRQ_WORKSPACE_MCP_URL